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![Dave Chinner](/assets/img/avatar_default.png)
There's a three-process deadlock involving shared/exclusive barriers and inverted lock orders in the directory readdir implementation. It's a pre-existing problem with lock ordering, exposed by the VFS parallelisation code. process 1 process 2 process 3 --------- --------- --------- readdir iolock(shared) get_leaf_dents iterate entries ilock(shared) map, lock and read buffer iunlock(shared) process entries in buffer ..... readdir iolock(shared) get_leaf_dents iterate entries ilock(shared) map, lock buffer <blocks> finish ->iterate_shared file_accessed() ->update_time start transaction ilock(excl) <blocks> ..... finishes processing buffer get next buffer ilock(shared) <blocks> And that's the deadlock. Fix this by dropping the current buffer lock in process 1 before trying to map the next buffer. This means we keep the lock order of ilock -> buffer lock intact and hence will allow process 3 to make progress and drop it's ilock(shared) once it is done. Reported-by: Xiong Zhou <xzhou@redhat.com> Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
691 lines
18 KiB
C
691 lines
18 KiB
C
/*
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* Copyright (c) 2000-2005 Silicon Graphics, Inc.
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* Copyright (c) 2013 Red Hat, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "xfs.h"
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#include "xfs_fs.h"
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#include "xfs_format.h"
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#include "xfs_log_format.h"
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#include "xfs_trans_resv.h"
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#include "xfs_bit.h"
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#include "xfs_mount.h"
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#include "xfs_da_format.h"
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#include "xfs_da_btree.h"
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#include "xfs_inode.h"
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#include "xfs_dir2.h"
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#include "xfs_dir2_priv.h"
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#include "xfs_error.h"
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#include "xfs_trace.h"
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#include "xfs_bmap.h"
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#include "xfs_trans.h"
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/*
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* Directory file type support functions
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*/
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static unsigned char xfs_dir3_filetype_table[] = {
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DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
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DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
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};
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static unsigned char
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xfs_dir3_get_dtype(
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struct xfs_mount *mp,
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__uint8_t filetype)
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{
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if (!xfs_sb_version_hasftype(&mp->m_sb))
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return DT_UNKNOWN;
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if (filetype >= XFS_DIR3_FT_MAX)
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return DT_UNKNOWN;
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return xfs_dir3_filetype_table[filetype];
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}
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STATIC int
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xfs_dir2_sf_getdents(
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struct xfs_da_args *args,
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struct dir_context *ctx)
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{
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int i; /* shortform entry number */
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struct xfs_inode *dp = args->dp; /* incore directory inode */
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xfs_dir2_dataptr_t off; /* current entry's offset */
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xfs_dir2_sf_entry_t *sfep; /* shortform directory entry */
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xfs_dir2_sf_hdr_t *sfp; /* shortform structure */
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xfs_dir2_dataptr_t dot_offset;
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xfs_dir2_dataptr_t dotdot_offset;
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xfs_ino_t ino;
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struct xfs_da_geometry *geo = args->geo;
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ASSERT(dp->i_df.if_flags & XFS_IFINLINE);
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/*
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* Give up if the directory is way too short.
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*/
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if (dp->i_d.di_size < offsetof(xfs_dir2_sf_hdr_t, parent)) {
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ASSERT(XFS_FORCED_SHUTDOWN(dp->i_mount));
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return -EIO;
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}
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ASSERT(dp->i_df.if_bytes == dp->i_d.di_size);
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ASSERT(dp->i_df.if_u1.if_data != NULL);
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sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
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ASSERT(dp->i_d.di_size >= xfs_dir2_sf_hdr_size(sfp->i8count));
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/*
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* If the block number in the offset is out of range, we're done.
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*/
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if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
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return 0;
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/*
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* Precalculate offsets for . and .. as we will always need them.
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*
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* XXX(hch): the second argument is sometimes 0 and sometimes
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* geo->datablk
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*/
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dot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
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dp->d_ops->data_dot_offset);
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dotdot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
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dp->d_ops->data_dotdot_offset);
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/*
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* Put . entry unless we're starting past it.
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*/
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if (ctx->pos <= dot_offset) {
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ctx->pos = dot_offset & 0x7fffffff;
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if (!dir_emit(ctx, ".", 1, dp->i_ino, DT_DIR))
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return 0;
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}
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/*
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* Put .. entry unless we're starting past it.
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*/
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if (ctx->pos <= dotdot_offset) {
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ino = dp->d_ops->sf_get_parent_ino(sfp);
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ctx->pos = dotdot_offset & 0x7fffffff;
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if (!dir_emit(ctx, "..", 2, ino, DT_DIR))
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return 0;
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}
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/*
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* Loop while there are more entries and put'ing works.
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*/
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sfep = xfs_dir2_sf_firstentry(sfp);
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for (i = 0; i < sfp->count; i++) {
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__uint8_t filetype;
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off = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
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xfs_dir2_sf_get_offset(sfep));
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if (ctx->pos > off) {
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sfep = dp->d_ops->sf_nextentry(sfp, sfep);
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continue;
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}
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ino = dp->d_ops->sf_get_ino(sfp, sfep);
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filetype = dp->d_ops->sf_get_ftype(sfep);
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ctx->pos = off & 0x7fffffff;
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if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
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xfs_dir3_get_dtype(dp->i_mount, filetype)))
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return 0;
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sfep = dp->d_ops->sf_nextentry(sfp, sfep);
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}
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ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
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0x7fffffff;
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return 0;
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}
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/*
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* Readdir for block directories.
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*/
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STATIC int
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xfs_dir2_block_getdents(
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struct xfs_da_args *args,
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struct dir_context *ctx)
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{
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struct xfs_inode *dp = args->dp; /* incore directory inode */
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xfs_dir2_data_hdr_t *hdr; /* block header */
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struct xfs_buf *bp; /* buffer for block */
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xfs_dir2_block_tail_t *btp; /* block tail */
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xfs_dir2_data_entry_t *dep; /* block data entry */
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xfs_dir2_data_unused_t *dup; /* block unused entry */
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char *endptr; /* end of the data entries */
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int error; /* error return value */
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char *ptr; /* current data entry */
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int wantoff; /* starting block offset */
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xfs_off_t cook;
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struct xfs_da_geometry *geo = args->geo;
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int lock_mode;
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/*
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* If the block number in the offset is out of range, we're done.
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*/
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if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
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return 0;
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lock_mode = xfs_ilock_data_map_shared(dp);
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error = xfs_dir3_block_read(NULL, dp, &bp);
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xfs_iunlock(dp, lock_mode);
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if (error)
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return error;
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/*
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* Extract the byte offset we start at from the seek pointer.
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* We'll skip entries before this.
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*/
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wantoff = xfs_dir2_dataptr_to_off(geo, ctx->pos);
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hdr = bp->b_addr;
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xfs_dir3_data_check(dp, bp);
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/*
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* Set up values for the loop.
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*/
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btp = xfs_dir2_block_tail_p(geo, hdr);
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ptr = (char *)dp->d_ops->data_entry_p(hdr);
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endptr = (char *)xfs_dir2_block_leaf_p(btp);
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/*
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* Loop over the data portion of the block.
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* Each object is a real entry (dep) or an unused one (dup).
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*/
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while (ptr < endptr) {
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__uint8_t filetype;
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dup = (xfs_dir2_data_unused_t *)ptr;
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/*
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* Unused, skip it.
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*/
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if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
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ptr += be16_to_cpu(dup->length);
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continue;
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}
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dep = (xfs_dir2_data_entry_t *)ptr;
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/*
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* Bump pointer for the next iteration.
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*/
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ptr += dp->d_ops->data_entsize(dep->namelen);
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/*
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* The entry is before the desired starting point, skip it.
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*/
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if ((char *)dep - (char *)hdr < wantoff)
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continue;
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cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
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(char *)dep - (char *)hdr);
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ctx->pos = cook & 0x7fffffff;
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filetype = dp->d_ops->data_get_ftype(dep);
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/*
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* If it didn't fit, set the final offset to here & return.
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*/
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if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
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be64_to_cpu(dep->inumber),
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xfs_dir3_get_dtype(dp->i_mount, filetype))) {
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xfs_trans_brelse(NULL, bp);
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return 0;
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}
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}
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/*
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* Reached the end of the block.
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* Set the offset to a non-existent block 1 and return.
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*/
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ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
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0x7fffffff;
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xfs_trans_brelse(NULL, bp);
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return 0;
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}
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struct xfs_dir2_leaf_map_info {
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xfs_extlen_t map_blocks; /* number of fsbs in map */
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xfs_dablk_t map_off; /* last mapped file offset */
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int map_size; /* total entries in *map */
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int map_valid; /* valid entries in *map */
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int nmap; /* mappings to ask xfs_bmapi */
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xfs_dir2_db_t curdb; /* db for current block */
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int ra_current; /* number of read-ahead blks */
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int ra_index; /* *map index for read-ahead */
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int ra_offset; /* map entry offset for ra */
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int ra_want; /* readahead count wanted */
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struct xfs_bmbt_irec map[]; /* map vector for blocks */
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};
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STATIC int
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xfs_dir2_leaf_readbuf(
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struct xfs_da_args *args,
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size_t bufsize,
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struct xfs_dir2_leaf_map_info *mip,
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xfs_dir2_off_t *curoff,
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struct xfs_buf **bpp,
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bool trim_map)
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{
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struct xfs_inode *dp = args->dp;
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struct xfs_buf *bp = NULL;
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struct xfs_bmbt_irec *map = mip->map;
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struct blk_plug plug;
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int error = 0;
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int length;
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int i;
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int j;
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struct xfs_da_geometry *geo = args->geo;
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/*
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* If the caller just finished processing a buffer, it will tell us
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* we need to trim that block out of the mapping now it is done.
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*/
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if (trim_map) {
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mip->map_blocks -= geo->fsbcount;
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/*
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* Loop to get rid of the extents for the
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* directory block.
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*/
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for (i = geo->fsbcount; i > 0; ) {
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j = min_t(int, map->br_blockcount, i);
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map->br_blockcount -= j;
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map->br_startblock += j;
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map->br_startoff += j;
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/*
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* If mapping is done, pitch it from
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* the table.
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*/
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if (!map->br_blockcount && --mip->map_valid)
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memmove(&map[0], &map[1],
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sizeof(map[0]) * mip->map_valid);
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i -= j;
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}
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}
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/*
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* Recalculate the readahead blocks wanted.
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*/
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mip->ra_want = howmany(bufsize + geo->blksize, (1 << geo->fsblog)) - 1;
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ASSERT(mip->ra_want >= 0);
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/*
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* If we don't have as many as we want, and we haven't
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* run out of data blocks, get some more mappings.
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*/
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if (1 + mip->ra_want > mip->map_blocks &&
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mip->map_off < xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET)) {
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/*
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* Get more bmaps, fill in after the ones
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* we already have in the table.
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*/
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mip->nmap = mip->map_size - mip->map_valid;
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error = xfs_bmapi_read(dp, mip->map_off,
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xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET) -
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mip->map_off,
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&map[mip->map_valid], &mip->nmap, 0);
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/*
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* Don't know if we should ignore this or try to return an
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* error. The trouble with returning errors is that readdir
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* will just stop without actually passing the error through.
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*/
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if (error)
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goto out; /* XXX */
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/*
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* If we got all the mappings we asked for, set the final map
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* offset based on the last bmap value received. Otherwise,
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* we've reached the end.
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*/
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if (mip->nmap == mip->map_size - mip->map_valid) {
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i = mip->map_valid + mip->nmap - 1;
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mip->map_off = map[i].br_startoff + map[i].br_blockcount;
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} else
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mip->map_off = xfs_dir2_byte_to_da(geo,
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XFS_DIR2_LEAF_OFFSET);
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/*
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* Look for holes in the mapping, and eliminate them. Count up
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* the valid blocks.
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*/
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for (i = mip->map_valid; i < mip->map_valid + mip->nmap; ) {
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if (map[i].br_startblock == HOLESTARTBLOCK) {
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mip->nmap--;
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length = mip->map_valid + mip->nmap - i;
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if (length)
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memmove(&map[i], &map[i + 1],
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sizeof(map[i]) * length);
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} else {
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mip->map_blocks += map[i].br_blockcount;
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i++;
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}
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}
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mip->map_valid += mip->nmap;
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}
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/*
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* No valid mappings, so no more data blocks.
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*/
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if (!mip->map_valid) {
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*curoff = xfs_dir2_da_to_byte(geo, mip->map_off);
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goto out;
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}
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/*
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* Read the directory block starting at the first mapping.
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*/
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mip->curdb = xfs_dir2_da_to_db(geo, map->br_startoff);
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error = xfs_dir3_data_read(NULL, dp, map->br_startoff,
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map->br_blockcount >= geo->fsbcount ?
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XFS_FSB_TO_DADDR(dp->i_mount, map->br_startblock) :
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-1, &bp);
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/*
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* Should just skip over the data block instead of giving up.
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*/
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if (error)
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goto out; /* XXX */
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/*
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* Adjust the current amount of read-ahead: we just read a block that
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* was previously ra.
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*/
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if (mip->ra_current)
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mip->ra_current -= geo->fsbcount;
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/*
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* Do we need more readahead?
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*/
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blk_start_plug(&plug);
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for (mip->ra_index = mip->ra_offset = i = 0;
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mip->ra_want > mip->ra_current && i < mip->map_blocks;
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i += geo->fsbcount) {
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ASSERT(mip->ra_index < mip->map_valid);
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/*
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* Read-ahead a contiguous directory block.
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*/
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if (i > mip->ra_current &&
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map[mip->ra_index].br_blockcount >= geo->fsbcount) {
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xfs_dir3_data_readahead(dp,
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map[mip->ra_index].br_startoff + mip->ra_offset,
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XFS_FSB_TO_DADDR(dp->i_mount,
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map[mip->ra_index].br_startblock +
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mip->ra_offset));
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mip->ra_current = i;
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}
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/*
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* Read-ahead a non-contiguous directory block. This doesn't
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* use our mapping, but this is a very rare case.
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*/
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else if (i > mip->ra_current) {
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xfs_dir3_data_readahead(dp,
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map[mip->ra_index].br_startoff +
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mip->ra_offset, -1);
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mip->ra_current = i;
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}
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/*
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* Advance offset through the mapping table.
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*/
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for (j = 0; j < geo->fsbcount; j += length ) {
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/*
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* The rest of this extent but not more than a dir
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* block.
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*/
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length = min_t(int, geo->fsbcount,
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map[mip->ra_index].br_blockcount -
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mip->ra_offset);
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mip->ra_offset += length;
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/*
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* Advance to the next mapping if this one is used up.
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*/
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if (mip->ra_offset == map[mip->ra_index].br_blockcount) {
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mip->ra_offset = 0;
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mip->ra_index++;
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}
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}
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}
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blk_finish_plug(&plug);
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out:
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*bpp = bp;
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return error;
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}
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/*
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* Getdents (readdir) for leaf and node directories.
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* This reads the data blocks only, so is the same for both forms.
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*/
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STATIC int
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xfs_dir2_leaf_getdents(
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struct xfs_da_args *args,
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struct dir_context *ctx,
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size_t bufsize)
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{
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struct xfs_inode *dp = args->dp;
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struct xfs_buf *bp = NULL; /* data block buffer */
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xfs_dir2_data_hdr_t *hdr; /* data block header */
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xfs_dir2_data_entry_t *dep; /* data entry */
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xfs_dir2_data_unused_t *dup; /* unused entry */
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int error = 0; /* error return value */
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int length; /* temporary length value */
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int byteoff; /* offset in current block */
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xfs_dir2_off_t curoff; /* current overall offset */
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xfs_dir2_off_t newoff; /* new curoff after new blk */
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char *ptr = NULL; /* pointer to current data */
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struct xfs_dir2_leaf_map_info *map_info;
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struct xfs_da_geometry *geo = args->geo;
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|
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/*
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* If the offset is at or past the largest allowed value,
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* give up right away.
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*/
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if (ctx->pos >= XFS_DIR2_MAX_DATAPTR)
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return 0;
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|
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/*
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* Set up to bmap a number of blocks based on the caller's
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* buffer size, the directory block size, and the filesystem
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* block size.
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*/
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length = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
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map_info = kmem_zalloc(offsetof(struct xfs_dir2_leaf_map_info, map) +
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(length * sizeof(struct xfs_bmbt_irec)),
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KM_SLEEP | KM_NOFS);
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map_info->map_size = length;
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|
|
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/*
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* Inside the loop we keep the main offset value as a byte offset
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* in the directory file.
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|
*/
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|
curoff = xfs_dir2_dataptr_to_byte(ctx->pos);
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|
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/*
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* Force this conversion through db so we truncate the offset
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|
* down to get the start of the data block.
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|
*/
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|
map_info->map_off = xfs_dir2_db_to_da(geo,
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xfs_dir2_byte_to_db(geo, curoff));
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|
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/*
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* Loop over directory entries until we reach the end offset.
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* Get more blocks and readahead as necessary.
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|
*/
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while (curoff < XFS_DIR2_LEAF_OFFSET) {
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__uint8_t filetype;
|
|
|
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/*
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* If we have no buffer, or we're off the end of the
|
|
* current buffer, need to get another one.
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|
*/
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if (!bp || ptr >= (char *)bp->b_addr + geo->blksize) {
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int lock_mode;
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bool trim_map = false;
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|
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if (bp) {
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xfs_trans_brelse(NULL, bp);
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bp = NULL;
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trim_map = true;
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}
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|
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lock_mode = xfs_ilock_data_map_shared(dp);
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error = xfs_dir2_leaf_readbuf(args, bufsize, map_info,
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&curoff, &bp, trim_map);
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xfs_iunlock(dp, lock_mode);
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if (error || !map_info->map_valid)
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|
break;
|
|
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|
/*
|
|
* Having done a read, we need to set a new offset.
|
|
*/
|
|
newoff = xfs_dir2_db_off_to_byte(geo,
|
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map_info->curdb, 0);
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/*
|
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* Start of the current block.
|
|
*/
|
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if (curoff < newoff)
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curoff = newoff;
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/*
|
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* Make sure we're in the right block.
|
|
*/
|
|
else if (curoff > newoff)
|
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ASSERT(xfs_dir2_byte_to_db(geo, curoff) ==
|
|
map_info->curdb);
|
|
hdr = bp->b_addr;
|
|
xfs_dir3_data_check(dp, bp);
|
|
/*
|
|
* Find our position in the block.
|
|
*/
|
|
ptr = (char *)dp->d_ops->data_entry_p(hdr);
|
|
byteoff = xfs_dir2_byte_to_off(geo, curoff);
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|
/*
|
|
* Skip past the header.
|
|
*/
|
|
if (byteoff == 0)
|
|
curoff += dp->d_ops->data_entry_offset;
|
|
/*
|
|
* Skip past entries until we reach our offset.
|
|
*/
|
|
else {
|
|
while ((char *)ptr - (char *)hdr < byteoff) {
|
|
dup = (xfs_dir2_data_unused_t *)ptr;
|
|
|
|
if (be16_to_cpu(dup->freetag)
|
|
== XFS_DIR2_DATA_FREE_TAG) {
|
|
|
|
length = be16_to_cpu(dup->length);
|
|
ptr += length;
|
|
continue;
|
|
}
|
|
dep = (xfs_dir2_data_entry_t *)ptr;
|
|
length =
|
|
dp->d_ops->data_entsize(dep->namelen);
|
|
ptr += length;
|
|
}
|
|
/*
|
|
* Now set our real offset.
|
|
*/
|
|
curoff =
|
|
xfs_dir2_db_off_to_byte(geo,
|
|
xfs_dir2_byte_to_db(geo, curoff),
|
|
(char *)ptr - (char *)hdr);
|
|
if (ptr >= (char *)hdr + geo->blksize) {
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
/*
|
|
* We have a pointer to an entry.
|
|
* Is it a live one?
|
|
*/
|
|
dup = (xfs_dir2_data_unused_t *)ptr;
|
|
/*
|
|
* No, it's unused, skip over it.
|
|
*/
|
|
if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
|
|
length = be16_to_cpu(dup->length);
|
|
ptr += length;
|
|
curoff += length;
|
|
continue;
|
|
}
|
|
|
|
dep = (xfs_dir2_data_entry_t *)ptr;
|
|
length = dp->d_ops->data_entsize(dep->namelen);
|
|
filetype = dp->d_ops->data_get_ftype(dep);
|
|
|
|
ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
|
|
if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
|
|
be64_to_cpu(dep->inumber),
|
|
xfs_dir3_get_dtype(dp->i_mount, filetype)))
|
|
break;
|
|
|
|
/*
|
|
* Advance to next entry in the block.
|
|
*/
|
|
ptr += length;
|
|
curoff += length;
|
|
/* bufsize may have just been a guess; don't go negative */
|
|
bufsize = bufsize > length ? bufsize - length : 0;
|
|
}
|
|
|
|
/*
|
|
* All done. Set output offset value to current offset.
|
|
*/
|
|
if (curoff > xfs_dir2_dataptr_to_byte(XFS_DIR2_MAX_DATAPTR))
|
|
ctx->pos = XFS_DIR2_MAX_DATAPTR & 0x7fffffff;
|
|
else
|
|
ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
|
|
kmem_free(map_info);
|
|
if (bp)
|
|
xfs_trans_brelse(NULL, bp);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Read a directory.
|
|
*/
|
|
int
|
|
xfs_readdir(
|
|
struct xfs_inode *dp,
|
|
struct dir_context *ctx,
|
|
size_t bufsize)
|
|
{
|
|
struct xfs_da_args args = { NULL };
|
|
int rval;
|
|
int v;
|
|
|
|
trace_xfs_readdir(dp);
|
|
|
|
if (XFS_FORCED_SHUTDOWN(dp->i_mount))
|
|
return -EIO;
|
|
|
|
ASSERT(S_ISDIR(VFS_I(dp)->i_mode));
|
|
XFS_STATS_INC(dp->i_mount, xs_dir_getdents);
|
|
|
|
args.dp = dp;
|
|
args.geo = dp->i_mount->m_dir_geo;
|
|
|
|
xfs_ilock(dp, XFS_IOLOCK_SHARED);
|
|
if (dp->i_d.di_format == XFS_DINODE_FMT_LOCAL)
|
|
rval = xfs_dir2_sf_getdents(&args, ctx);
|
|
else if ((rval = xfs_dir2_isblock(&args, &v)))
|
|
;
|
|
else if (v)
|
|
rval = xfs_dir2_block_getdents(&args, ctx);
|
|
else
|
|
rval = xfs_dir2_leaf_getdents(&args, ctx, bufsize);
|
|
xfs_iunlock(dp, XFS_IOLOCK_SHARED);
|
|
|
|
return rval;
|
|
}
|