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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-29 23:53:32 +00:00
372a03e018
Ext4 needs to serialize unaligned direct AIO because the zeroing of
partial blocks of two competing unaligned AIOs can result in data
corruption.
However it decides not to serialize if the potentially unaligned aio is
past i_size with the rationale that no pending writes are possible past
i_size. Unfortunately if the i_size is not block aligned and the second
unaligned write lands past i_size, but still into the same block, it has
the potential of corrupting the previous unaligned write to the same
block.
This is (very simplified) reproducer from Frank
// 41472 = (10 * 4096) + 512
// 37376 = 41472 - 4096
ftruncate(fd, 41472);
io_prep_pwrite(iocbs[0], fd, buf[0], 4096, 37376);
io_prep_pwrite(iocbs[1], fd, buf[1], 4096, 41472);
io_submit(io_ctx, 1, &iocbs[1]);
io_submit(io_ctx, 1, &iocbs[2]);
io_getevents(io_ctx, 2, 2, events, NULL);
Without this patch the 512B range from 40960 up to the start of the
second unaligned write (41472) is going to be zeroed overwriting the data
written by the first write. This is a data corruption.
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
00009200 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30
*
0000a000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0000a200 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
With this patch the data corruption is avoided because we will recognize
the unaligned_aio and wait for the unwritten extent conversion.
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
00009200 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30
*
0000a200 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
*
0000b200
Reported-by: Frank Sorenson <fsorenso@redhat.com>
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Fixes: e9e3bcecf4
("ext4: serialize unaligned asynchronous DIO")
Cc: stable@vger.kernel.org
524 lines
13 KiB
C
524 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/ext4/file.c
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*
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* Copyright (C) 1992, 1993, 1994, 1995
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* Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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*
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* from
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*
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* linux/fs/minix/file.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext4 fs regular file handling primitives
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*
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* 64-bit file support on 64-bit platforms by Jakub Jelinek
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* (jj@sunsite.ms.mff.cuni.cz)
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*/
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/iomap.h>
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#include <linux/mount.h>
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#include <linux/path.h>
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#include <linux/dax.h>
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#include <linux/quotaops.h>
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#include <linux/pagevec.h>
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#include <linux/uio.h>
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#include <linux/mman.h>
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#include "ext4.h"
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#include "ext4_jbd2.h"
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#include "xattr.h"
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#include "acl.h"
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#ifdef CONFIG_FS_DAX
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static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
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{
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struct inode *inode = file_inode(iocb->ki_filp);
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ssize_t ret;
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if (!inode_trylock_shared(inode)) {
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if (iocb->ki_flags & IOCB_NOWAIT)
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return -EAGAIN;
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inode_lock_shared(inode);
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}
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/*
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* Recheck under inode lock - at this point we are sure it cannot
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* change anymore
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*/
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if (!IS_DAX(inode)) {
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inode_unlock_shared(inode);
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/* Fallback to buffered IO in case we cannot support DAX */
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return generic_file_read_iter(iocb, to);
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}
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ret = dax_iomap_rw(iocb, to, &ext4_iomap_ops);
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inode_unlock_shared(inode);
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file_accessed(iocb->ki_filp);
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return ret;
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}
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#endif
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static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
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{
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if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb))))
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return -EIO;
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if (!iov_iter_count(to))
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return 0; /* skip atime */
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#ifdef CONFIG_FS_DAX
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if (IS_DAX(file_inode(iocb->ki_filp)))
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return ext4_dax_read_iter(iocb, to);
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#endif
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return generic_file_read_iter(iocb, to);
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}
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/*
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* Called when an inode is released. Note that this is different
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* from ext4_file_open: open gets called at every open, but release
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* gets called only when /all/ the files are closed.
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*/
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static int ext4_release_file(struct inode *inode, struct file *filp)
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{
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if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
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ext4_alloc_da_blocks(inode);
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ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
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}
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/* if we are the last writer on the inode, drop the block reservation */
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if ((filp->f_mode & FMODE_WRITE) &&
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(atomic_read(&inode->i_writecount) == 1) &&
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!EXT4_I(inode)->i_reserved_data_blocks)
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{
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down_write(&EXT4_I(inode)->i_data_sem);
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ext4_discard_preallocations(inode);
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up_write(&EXT4_I(inode)->i_data_sem);
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}
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if (is_dx(inode) && filp->private_data)
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ext4_htree_free_dir_info(filp->private_data);
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return 0;
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}
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static void ext4_unwritten_wait(struct inode *inode)
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{
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wait_queue_head_t *wq = ext4_ioend_wq(inode);
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wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
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}
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/*
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* This tests whether the IO in question is block-aligned or not.
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* Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
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* are converted to written only after the IO is complete. Until they are
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* mapped, these blocks appear as holes, so dio_zero_block() will assume that
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* it needs to zero out portions of the start and/or end block. If 2 AIO
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* threads are at work on the same unwritten block, they must be synchronized
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* or one thread will zero the other's data, causing corruption.
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*/
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static int
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ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
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{
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struct super_block *sb = inode->i_sb;
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int blockmask = sb->s_blocksize - 1;
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if (pos >= ALIGN(i_size_read(inode), sb->s_blocksize))
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return 0;
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if ((pos | iov_iter_alignment(from)) & blockmask)
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return 1;
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return 0;
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}
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/* Is IO overwriting allocated and initialized blocks? */
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static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
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{
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struct ext4_map_blocks map;
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unsigned int blkbits = inode->i_blkbits;
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int err, blklen;
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if (pos + len > i_size_read(inode))
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return false;
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map.m_lblk = pos >> blkbits;
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map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
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blklen = map.m_len;
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err = ext4_map_blocks(NULL, inode, &map, 0);
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/*
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* 'err==len' means that all of the blocks have been preallocated,
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* regardless of whether they have been initialized or not. To exclude
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* unwritten extents, we need to check m_flags.
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*/
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return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
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}
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static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
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{
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struct inode *inode = file_inode(iocb->ki_filp);
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ssize_t ret;
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ret = generic_write_checks(iocb, from);
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if (ret <= 0)
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return ret;
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/*
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* If we have encountered a bitmap-format file, the size limit
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* is smaller than s_maxbytes, which is for extent-mapped files.
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*/
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if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
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struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
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if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
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return -EFBIG;
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iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
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}
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return iov_iter_count(from);
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}
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#ifdef CONFIG_FS_DAX
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static ssize_t
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ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
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{
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struct inode *inode = file_inode(iocb->ki_filp);
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ssize_t ret;
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if (!inode_trylock(inode)) {
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if (iocb->ki_flags & IOCB_NOWAIT)
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return -EAGAIN;
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inode_lock(inode);
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}
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ret = ext4_write_checks(iocb, from);
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if (ret <= 0)
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goto out;
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ret = file_remove_privs(iocb->ki_filp);
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if (ret)
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goto out;
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ret = file_update_time(iocb->ki_filp);
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if (ret)
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goto out;
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ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
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out:
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inode_unlock(inode);
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if (ret > 0)
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ret = generic_write_sync(iocb, ret);
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return ret;
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}
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#endif
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static ssize_t
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ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
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{
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struct inode *inode = file_inode(iocb->ki_filp);
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int o_direct = iocb->ki_flags & IOCB_DIRECT;
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int unaligned_aio = 0;
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int overwrite = 0;
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ssize_t ret;
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if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
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return -EIO;
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#ifdef CONFIG_FS_DAX
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if (IS_DAX(inode))
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return ext4_dax_write_iter(iocb, from);
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#endif
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if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
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return -EOPNOTSUPP;
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if (!inode_trylock(inode)) {
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if (iocb->ki_flags & IOCB_NOWAIT)
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return -EAGAIN;
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inode_lock(inode);
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}
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ret = ext4_write_checks(iocb, from);
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if (ret <= 0)
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goto out;
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/*
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* Unaligned direct AIO must be serialized among each other as zeroing
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* of partial blocks of two competing unaligned AIOs can result in data
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* corruption.
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*/
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if (o_direct && ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
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!is_sync_kiocb(iocb) &&
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ext4_unaligned_aio(inode, from, iocb->ki_pos)) {
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unaligned_aio = 1;
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ext4_unwritten_wait(inode);
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}
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iocb->private = &overwrite;
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/* Check whether we do a DIO overwrite or not */
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if (o_direct && !unaligned_aio) {
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if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
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if (ext4_should_dioread_nolock(inode))
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overwrite = 1;
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} else if (iocb->ki_flags & IOCB_NOWAIT) {
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ret = -EAGAIN;
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goto out;
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}
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}
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ret = __generic_file_write_iter(iocb, from);
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inode_unlock(inode);
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if (ret > 0)
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ret = generic_write_sync(iocb, ret);
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return ret;
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out:
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inode_unlock(inode);
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return ret;
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}
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#ifdef CONFIG_FS_DAX
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static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
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enum page_entry_size pe_size)
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{
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int error = 0;
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vm_fault_t result;
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int retries = 0;
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handle_t *handle = NULL;
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struct inode *inode = file_inode(vmf->vma->vm_file);
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struct super_block *sb = inode->i_sb;
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/*
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* We have to distinguish real writes from writes which will result in a
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* COW page; COW writes should *not* poke the journal (the file will not
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* be changed). Doing so would cause unintended failures when mounted
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* read-only.
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*
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* We check for VM_SHARED rather than vmf->cow_page since the latter is
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* unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
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* other sizes, dax_iomap_fault will handle splitting / fallback so that
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* we eventually come back with a COW page.
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*/
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bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
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(vmf->vma->vm_flags & VM_SHARED);
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pfn_t pfn;
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if (write) {
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sb_start_pagefault(sb);
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file_update_time(vmf->vma->vm_file);
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down_read(&EXT4_I(inode)->i_mmap_sem);
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retry:
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handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
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EXT4_DATA_TRANS_BLOCKS(sb));
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if (IS_ERR(handle)) {
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up_read(&EXT4_I(inode)->i_mmap_sem);
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sb_end_pagefault(sb);
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return VM_FAULT_SIGBUS;
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}
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} else {
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down_read(&EXT4_I(inode)->i_mmap_sem);
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}
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result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
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if (write) {
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ext4_journal_stop(handle);
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if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
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ext4_should_retry_alloc(sb, &retries))
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goto retry;
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/* Handling synchronous page fault? */
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if (result & VM_FAULT_NEEDDSYNC)
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result = dax_finish_sync_fault(vmf, pe_size, pfn);
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up_read(&EXT4_I(inode)->i_mmap_sem);
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sb_end_pagefault(sb);
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} else {
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up_read(&EXT4_I(inode)->i_mmap_sem);
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}
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return result;
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}
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static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
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{
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return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
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}
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static const struct vm_operations_struct ext4_dax_vm_ops = {
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.fault = ext4_dax_fault,
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.huge_fault = ext4_dax_huge_fault,
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.page_mkwrite = ext4_dax_fault,
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.pfn_mkwrite = ext4_dax_fault,
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};
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#else
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#define ext4_dax_vm_ops ext4_file_vm_ops
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#endif
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static const struct vm_operations_struct ext4_file_vm_ops = {
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.fault = ext4_filemap_fault,
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.map_pages = filemap_map_pages,
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.page_mkwrite = ext4_page_mkwrite,
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};
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static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
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{
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struct inode *inode = file->f_mapping->host;
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if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
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return -EIO;
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/*
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* We don't support synchronous mappings for non-DAX files. At least
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* until someone comes with a sensible use case.
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*/
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if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC))
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return -EOPNOTSUPP;
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file_accessed(file);
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if (IS_DAX(file_inode(file))) {
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vma->vm_ops = &ext4_dax_vm_ops;
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vma->vm_flags |= VM_HUGEPAGE;
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} else {
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vma->vm_ops = &ext4_file_vm_ops;
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}
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return 0;
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}
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static int ext4_sample_last_mounted(struct super_block *sb,
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struct vfsmount *mnt)
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{
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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struct path path;
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char buf[64], *cp;
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handle_t *handle;
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int err;
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if (likely(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED))
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return 0;
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if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
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return 0;
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sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
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/*
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* Sample where the filesystem has been mounted and
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* store it in the superblock for sysadmin convenience
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* when trying to sort through large numbers of block
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* devices or filesystem images.
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*/
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memset(buf, 0, sizeof(buf));
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path.mnt = mnt;
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path.dentry = mnt->mnt_root;
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cp = d_path(&path, buf, sizeof(buf));
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err = 0;
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if (IS_ERR(cp))
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goto out;
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handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
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err = PTR_ERR(handle);
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if (IS_ERR(handle))
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goto out;
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BUFFER_TRACE(sbi->s_sbh, "get_write_access");
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err = ext4_journal_get_write_access(handle, sbi->s_sbh);
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if (err)
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goto out_journal;
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strlcpy(sbi->s_es->s_last_mounted, cp,
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sizeof(sbi->s_es->s_last_mounted));
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ext4_handle_dirty_super(handle, sb);
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out_journal:
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ext4_journal_stop(handle);
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out:
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sb_end_intwrite(sb);
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return err;
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}
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static int ext4_file_open(struct inode * inode, struct file * filp)
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{
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int ret;
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if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
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return -EIO;
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ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
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if (ret)
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return ret;
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ret = fscrypt_file_open(inode, filp);
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if (ret)
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|
return ret;
|
|
|
|
/*
|
|
* Set up the jbd2_inode if we are opening the inode for
|
|
* writing and the journal is present
|
|
*/
|
|
if (filp->f_mode & FMODE_WRITE) {
|
|
ret = ext4_inode_attach_jinode(inode);
|
|
if (ret < 0)
|
|
return ret;
|
|
}
|
|
|
|
filp->f_mode |= FMODE_NOWAIT;
|
|
return dquot_file_open(inode, filp);
|
|
}
|
|
|
|
/*
|
|
* ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
|
|
* by calling generic_file_llseek_size() with the appropriate maxbytes
|
|
* value for each.
|
|
*/
|
|
loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
|
|
{
|
|
struct inode *inode = file->f_mapping->host;
|
|
loff_t maxbytes;
|
|
|
|
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
|
|
maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
|
|
else
|
|
maxbytes = inode->i_sb->s_maxbytes;
|
|
|
|
switch (whence) {
|
|
default:
|
|
return generic_file_llseek_size(file, offset, whence,
|
|
maxbytes, i_size_read(inode));
|
|
case SEEK_HOLE:
|
|
inode_lock_shared(inode);
|
|
offset = iomap_seek_hole(inode, offset, &ext4_iomap_ops);
|
|
inode_unlock_shared(inode);
|
|
break;
|
|
case SEEK_DATA:
|
|
inode_lock_shared(inode);
|
|
offset = iomap_seek_data(inode, offset, &ext4_iomap_ops);
|
|
inode_unlock_shared(inode);
|
|
break;
|
|
}
|
|
|
|
if (offset < 0)
|
|
return offset;
|
|
return vfs_setpos(file, offset, maxbytes);
|
|
}
|
|
|
|
const struct file_operations ext4_file_operations = {
|
|
.llseek = ext4_llseek,
|
|
.read_iter = ext4_file_read_iter,
|
|
.write_iter = ext4_file_write_iter,
|
|
.unlocked_ioctl = ext4_ioctl,
|
|
#ifdef CONFIG_COMPAT
|
|
.compat_ioctl = ext4_compat_ioctl,
|
|
#endif
|
|
.mmap = ext4_file_mmap,
|
|
.mmap_supported_flags = MAP_SYNC,
|
|
.open = ext4_file_open,
|
|
.release = ext4_release_file,
|
|
.fsync = ext4_sync_file,
|
|
.get_unmapped_area = thp_get_unmapped_area,
|
|
.splice_read = generic_file_splice_read,
|
|
.splice_write = iter_file_splice_write,
|
|
.fallocate = ext4_fallocate,
|
|
};
|
|
|
|
const struct inode_operations ext4_file_inode_operations = {
|
|
.setattr = ext4_setattr,
|
|
.getattr = ext4_file_getattr,
|
|
.listxattr = ext4_listxattr,
|
|
.get_acl = ext4_get_acl,
|
|
.set_acl = ext4_set_acl,
|
|
.fiemap = ext4_fiemap,
|
|
};
|
|
|