linux-stable/fs/xfs/xfs_dir2_readdir.c
Darrick J. Wong 65552b02a1 xfs: take the ILOCK when readdir inspects directory mapping data
I was poking around in the directory code while diagnosing online fsck
bugs, and noticed that xfs_readdir doesn't actually take the directory
ILOCK when it calls xfs_dir2_isblock.  xfs_dir_open most probably loaded
the data fork mappings and the VFS took i_rwsem (aka IOLOCK_SHARED) so
we're protected against writer threads, but we really need to follow the
locking model like we do in other places.

To avoid unnecessarily cycling the ILOCK for fairly small directories,
change the block/leaf _getdents functions to consume the ILOCK hold that
the parent readdir function took to decide on a _getdents implementation.

It is ok to cycle the ILOCK in readdir because the VFS takes the IOLOCK
in the appropriate mode during lookups and writes, and we don't want to
be holding the ILOCK when we copy directory entries to userspace in case
there's a page fault.  We really only need it to protect against data
fork lookups, like we do for other files.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
2022-01-11 15:11:04 -08:00

550 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2005 Silicon Graphics, Inc.
* Copyright (c) 2013 Red Hat, Inc.
* All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_trace.h"
#include "xfs_bmap.h"
#include "xfs_trans.h"
#include "xfs_error.h"
/*
* Directory file type support functions
*/
static unsigned char xfs_dir3_filetype_table[] = {
DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
};
unsigned char
xfs_dir3_get_dtype(
struct xfs_mount *mp,
uint8_t filetype)
{
if (!xfs_has_ftype(mp))
return DT_UNKNOWN;
if (filetype >= XFS_DIR3_FT_MAX)
return DT_UNKNOWN;
return xfs_dir3_filetype_table[filetype];
}
STATIC int
xfs_dir2_sf_getdents(
struct xfs_da_args *args,
struct dir_context *ctx)
{
int i; /* shortform entry number */
struct xfs_inode *dp = args->dp; /* incore directory inode */
struct xfs_mount *mp = dp->i_mount;
xfs_dir2_dataptr_t off; /* current entry's offset */
xfs_dir2_sf_entry_t *sfep; /* shortform directory entry */
xfs_dir2_sf_hdr_t *sfp; /* shortform structure */
xfs_dir2_dataptr_t dot_offset;
xfs_dir2_dataptr_t dotdot_offset;
xfs_ino_t ino;
struct xfs_da_geometry *geo = args->geo;
ASSERT(dp->i_df.if_format == XFS_DINODE_FMT_LOCAL);
ASSERT(dp->i_df.if_bytes == dp->i_disk_size);
ASSERT(dp->i_df.if_u1.if_data != NULL);
sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
/*
* If the block number in the offset is out of range, we're done.
*/
if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
return 0;
/*
* Precalculate offsets for "." and ".." as we will always need them.
* This relies on the fact that directories always start with the
* entries for "." and "..".
*/
dot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
geo->data_entry_offset);
dotdot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
geo->data_entry_offset +
xfs_dir2_data_entsize(mp, sizeof(".") - 1));
/*
* Put . entry unless we're starting past it.
*/
if (ctx->pos <= dot_offset) {
ctx->pos = dot_offset & 0x7fffffff;
if (!dir_emit(ctx, ".", 1, dp->i_ino, DT_DIR))
return 0;
}
/*
* Put .. entry unless we're starting past it.
*/
if (ctx->pos <= dotdot_offset) {
ino = xfs_dir2_sf_get_parent_ino(sfp);
ctx->pos = dotdot_offset & 0x7fffffff;
if (!dir_emit(ctx, "..", 2, ino, DT_DIR))
return 0;
}
/*
* Loop while there are more entries and put'ing works.
*/
sfep = xfs_dir2_sf_firstentry(sfp);
for (i = 0; i < sfp->count; i++) {
uint8_t filetype;
off = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
xfs_dir2_sf_get_offset(sfep));
if (ctx->pos > off) {
sfep = xfs_dir2_sf_nextentry(mp, sfp, sfep);
continue;
}
ino = xfs_dir2_sf_get_ino(mp, sfp, sfep);
filetype = xfs_dir2_sf_get_ftype(mp, sfep);
ctx->pos = off & 0x7fffffff;
if (XFS_IS_CORRUPT(dp->i_mount,
!xfs_dir2_namecheck(sfep->name,
sfep->namelen)))
return -EFSCORRUPTED;
if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
xfs_dir3_get_dtype(mp, filetype)))
return 0;
sfep = xfs_dir2_sf_nextentry(mp, sfp, sfep);
}
ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
0x7fffffff;
return 0;
}
/*
* Readdir for block directories.
*/
STATIC int
xfs_dir2_block_getdents(
struct xfs_da_args *args,
struct dir_context *ctx,
unsigned int *lock_mode)
{
struct xfs_inode *dp = args->dp; /* incore directory inode */
struct xfs_buf *bp; /* buffer for block */
int error; /* error return value */
int wantoff; /* starting block offset */
xfs_off_t cook;
struct xfs_da_geometry *geo = args->geo;
unsigned int offset, next_offset;
unsigned int end;
/*
* If the block number in the offset is out of range, we're done.
*/
if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
return 0;
error = xfs_dir3_block_read(args->trans, dp, &bp);
if (error)
return error;
xfs_iunlock(dp, *lock_mode);
*lock_mode = 0;
/*
* Extract the byte offset we start at from the seek pointer.
* We'll skip entries before this.
*/
wantoff = xfs_dir2_dataptr_to_off(geo, ctx->pos);
xfs_dir3_data_check(dp, bp);
/*
* Loop over the data portion of the block.
* Each object is a real entry (dep) or an unused one (dup).
*/
end = xfs_dir3_data_end_offset(geo, bp->b_addr);
for (offset = geo->data_entry_offset;
offset < end;
offset = next_offset) {
struct xfs_dir2_data_unused *dup = bp->b_addr + offset;
struct xfs_dir2_data_entry *dep = bp->b_addr + offset;
uint8_t filetype;
/*
* Unused, skip it.
*/
if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
next_offset = offset + be16_to_cpu(dup->length);
continue;
}
/*
* Bump pointer for the next iteration.
*/
next_offset = offset +
xfs_dir2_data_entsize(dp->i_mount, dep->namelen);
/*
* The entry is before the desired starting point, skip it.
*/
if (offset < wantoff)
continue;
cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk, offset);
ctx->pos = cook & 0x7fffffff;
filetype = xfs_dir2_data_get_ftype(dp->i_mount, dep);
/*
* If it didn't fit, set the final offset to here & return.
*/
if (XFS_IS_CORRUPT(dp->i_mount,
!xfs_dir2_namecheck(dep->name,
dep->namelen))) {
error = -EFSCORRUPTED;
goto out_rele;
}
if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
be64_to_cpu(dep->inumber),
xfs_dir3_get_dtype(dp->i_mount, filetype)))
goto out_rele;
}
/*
* Reached the end of the block.
* Set the offset to a non-existent block 1 and return.
*/
ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
0x7fffffff;
out_rele:
xfs_trans_brelse(args->trans, bp);
return error;
}
/*
* Read a directory block and initiate readahead for blocks beyond that.
* We maintain a sliding readahead window of the remaining space in the
* buffer rounded up to the nearest block.
*/
STATIC int
xfs_dir2_leaf_readbuf(
struct xfs_da_args *args,
size_t bufsize,
xfs_dir2_off_t *cur_off,
xfs_dablk_t *ra_blk,
struct xfs_buf **bpp)
{
struct xfs_inode *dp = args->dp;
struct xfs_buf *bp = NULL;
struct xfs_da_geometry *geo = args->geo;
struct xfs_ifork *ifp = XFS_IFORK_PTR(dp, XFS_DATA_FORK);
struct xfs_bmbt_irec map;
struct blk_plug plug;
xfs_dir2_off_t new_off;
xfs_dablk_t next_ra;
xfs_dablk_t map_off;
xfs_dablk_t last_da;
struct xfs_iext_cursor icur;
int ra_want;
int error = 0;
error = xfs_iread_extents(args->trans, dp, XFS_DATA_FORK);
if (error)
goto out;
/*
* Look for mapped directory blocks at or above the current offset.
* Truncate down to the nearest directory block to start the scanning
* operation.
*/
last_da = xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET);
map_off = xfs_dir2_db_to_da(geo, xfs_dir2_byte_to_db(geo, *cur_off));
if (!xfs_iext_lookup_extent(dp, ifp, map_off, &icur, &map))
goto out;
if (map.br_startoff >= last_da)
goto out;
xfs_trim_extent(&map, map_off, last_da - map_off);
/* Read the directory block of that first mapping. */
new_off = xfs_dir2_da_to_byte(geo, map.br_startoff);
if (new_off > *cur_off)
*cur_off = new_off;
error = xfs_dir3_data_read(args->trans, dp, map.br_startoff, 0, &bp);
if (error)
goto out;
/*
* Start readahead for the next bufsize's worth of dir data blocks.
* We may have already issued readahead for some of that range;
* ra_blk tracks the last block we tried to read(ahead).
*/
ra_want = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
if (*ra_blk >= last_da)
goto out;
else if (*ra_blk == 0)
*ra_blk = map.br_startoff;
next_ra = map.br_startoff + geo->fsbcount;
if (next_ra >= last_da)
goto out_no_ra;
if (map.br_blockcount < geo->fsbcount &&
!xfs_iext_next_extent(ifp, &icur, &map))
goto out_no_ra;
if (map.br_startoff >= last_da)
goto out_no_ra;
xfs_trim_extent(&map, next_ra, last_da - next_ra);
/* Start ra for each dir (not fs) block that has a mapping. */
blk_start_plug(&plug);
while (ra_want > 0) {
next_ra = roundup((xfs_dablk_t)map.br_startoff, geo->fsbcount);
while (ra_want > 0 &&
next_ra < map.br_startoff + map.br_blockcount) {
if (next_ra >= last_da) {
*ra_blk = last_da;
break;
}
if (next_ra > *ra_blk) {
xfs_dir3_data_readahead(dp, next_ra,
XFS_DABUF_MAP_HOLE_OK);
*ra_blk = next_ra;
}
ra_want -= geo->fsbcount;
next_ra += geo->fsbcount;
}
if (!xfs_iext_next_extent(ifp, &icur, &map)) {
*ra_blk = last_da;
break;
}
}
blk_finish_plug(&plug);
out:
*bpp = bp;
return error;
out_no_ra:
*ra_blk = last_da;
goto out;
}
/*
* Getdents (readdir) for leaf and node directories.
* This reads the data blocks only, so is the same for both forms.
*/
STATIC int
xfs_dir2_leaf_getdents(
struct xfs_da_args *args,
struct dir_context *ctx,
size_t bufsize,
unsigned int *lock_mode)
{
struct xfs_inode *dp = args->dp;
struct xfs_mount *mp = dp->i_mount;
struct xfs_buf *bp = NULL; /* data block buffer */
xfs_dir2_data_entry_t *dep; /* data entry */
xfs_dir2_data_unused_t *dup; /* unused entry */
struct xfs_da_geometry *geo = args->geo;
xfs_dablk_t rablk = 0; /* current readahead block */
xfs_dir2_off_t curoff; /* current overall offset */
int length; /* temporary length value */
int byteoff; /* offset in current block */
unsigned int offset = 0;
int error = 0; /* error return value */
/*
* If the offset is at or past the largest allowed value,
* give up right away.
*/
if (ctx->pos >= XFS_DIR2_MAX_DATAPTR)
return 0;
/*
* Inside the loop we keep the main offset value as a byte offset
* in the directory file.
*/
curoff = xfs_dir2_dataptr_to_byte(ctx->pos);
/*
* Loop over directory entries until we reach the end offset.
* Get more blocks and readahead as necessary.
*/
while (curoff < XFS_DIR2_LEAF_OFFSET) {
uint8_t filetype;
/*
* If we have no buffer, or we're off the end of the
* current buffer, need to get another one.
*/
if (!bp || offset >= geo->blksize) {
if (bp) {
xfs_trans_brelse(args->trans, bp);
bp = NULL;
}
if (*lock_mode == 0)
*lock_mode = xfs_ilock_data_map_shared(dp);
error = xfs_dir2_leaf_readbuf(args, bufsize, &curoff,
&rablk, &bp);
if (error || !bp)
break;
xfs_iunlock(dp, *lock_mode);
*lock_mode = 0;
xfs_dir3_data_check(dp, bp);
/*
* Find our position in the block.
*/
offset = geo->data_entry_offset;
byteoff = xfs_dir2_byte_to_off(geo, curoff);
/*
* Skip past the header.
*/
if (byteoff == 0)
curoff += geo->data_entry_offset;
/*
* Skip past entries until we reach our offset.
*/
else {
while (offset < byteoff) {
dup = bp->b_addr + offset;
if (be16_to_cpu(dup->freetag)
== XFS_DIR2_DATA_FREE_TAG) {
length = be16_to_cpu(dup->length);
offset += length;
continue;
}
dep = bp->b_addr + offset;
length = xfs_dir2_data_entsize(mp,
dep->namelen);
offset += length;
}
/*
* Now set our real offset.
*/
curoff =
xfs_dir2_db_off_to_byte(geo,
xfs_dir2_byte_to_db(geo, curoff),
offset);
if (offset >= geo->blksize)
continue;
}
}
/*
* We have a pointer to an entry. Is it a live one?
*/
dup = bp->b_addr + offset;
/*
* No, it's unused, skip over it.
*/
if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
length = be16_to_cpu(dup->length);
offset += length;
curoff += length;
continue;
}
dep = bp->b_addr + offset;
length = xfs_dir2_data_entsize(mp, dep->namelen);
filetype = xfs_dir2_data_get_ftype(mp, dep);
ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
if (XFS_IS_CORRUPT(dp->i_mount,
!xfs_dir2_namecheck(dep->name,
dep->namelen))) {
error = -EFSCORRUPTED;
break;
}
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.
*/
offset += 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;
if (bp)
xfs_trans_brelse(args->trans, bp);
return error;
}
/*
* Read a directory.
*
* If supplied, the transaction collects locked dir buffers to avoid
* nested buffer deadlocks. This function does not dirty the
* transaction. The caller must hold the IOLOCK (shared or exclusive)
* before calling this function.
*/
int
xfs_readdir(
struct xfs_trans *tp,
struct xfs_inode *dp,
struct dir_context *ctx,
size_t bufsize)
{
struct xfs_da_args args = { NULL };
unsigned int lock_mode;
int isblock;
int error;
trace_xfs_readdir(dp);
if (xfs_is_shutdown(dp->i_mount))
return -EIO;
ASSERT(S_ISDIR(VFS_I(dp)->i_mode));
ASSERT(xfs_isilocked(dp, XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
XFS_STATS_INC(dp->i_mount, xs_dir_getdents);
args.dp = dp;
args.geo = dp->i_mount->m_dir_geo;
args.trans = tp;
if (dp->i_df.if_format == XFS_DINODE_FMT_LOCAL)
return xfs_dir2_sf_getdents(&args, ctx);
lock_mode = xfs_ilock_data_map_shared(dp);
error = xfs_dir2_isblock(&args, &isblock);
if (error)
goto out_unlock;
if (isblock) {
error = xfs_dir2_block_getdents(&args, ctx, &lock_mode);
goto out_unlock;
}
error = xfs_dir2_leaf_getdents(&args, ctx, bufsize, &lock_mode);
out_unlock:
if (lock_mode)
xfs_iunlock(dp, lock_mode);
return error;
}