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Date: Sat, 12 Apr 2014 13:02:41 -0400
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: viro@...IV.linux.org.uk, Theodore Ts'o <tytso@....edu>
Subject: [PATCH 5/5] ext4: add locking for O_APPEND writes
Al Viro pointed out that we need to make sure we only allow one
O_APPEND write to proceed at a time so that the the s_bitmap_maxbytes
check can be properly checked.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
fs/ext4/file.c | 46 +++++++++++++++++++++++++++++-----------------
1 file changed, 29 insertions(+), 17 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 7c8f483..c3824dd 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -98,24 +98,32 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(iocb->ki_filp);
struct blk_plug plug;
+ struct mutex *aio_mutex = NULL;
int o_direct = file->f_flags & O_DIRECT;
- int overwrite = 0;
+ int overwrite = 0, i_mutex_grabbed = 0;
size_t length = iov_length(iov, nr_segs);
ssize_t ret;
BUG_ON(iocb->ki_pos != pos);
+ if (file->f_flags & O_APPEND) {
+ mutex_lock(&inode->i_mutex);
+ i_mutex_grabbed = 1;
+ iocb->ki_pos = pos = i_size_read(inode);
+ }
+
/*
* If we have encountered a bitmap-format file, the size limit
* is smaller than s_maxbytes, which is for extent-mapped files.
*/
-
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
if ((pos > sbi->s_bitmap_maxbytes ||
- (pos == sbi->s_bitmap_maxbytes && length > 0)))
- return -EFBIG;
+ (pos == sbi->s_bitmap_maxbytes && length > 0))) {
+ ret = -EFBIG;
+ goto errout;
+ }
if (pos + length > sbi->s_bitmap_maxbytes) {
nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
@@ -123,19 +131,20 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
}
}
- if (o_direct) {
- struct mutex *aio_mutex = NULL;
-
- /* Unaligned direct AIO must be serialized; see comment above */
- if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
- !is_sync_kiocb(iocb) &&
- ext4_unaligned_aio(inode, iov, nr_segs, pos)) {
- aio_mutex = ext4_aio_mutex(inode);
- mutex_lock(aio_mutex);
- ext4_unwritten_wait(inode);
- }
+ /* Unaligned direct AIO must be serialized; see comment above */
+ if (o_direct && ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
+ !is_sync_kiocb(iocb) &&
+ ext4_unaligned_aio(inode, iov, nr_segs, pos)) {
+ aio_mutex = ext4_aio_mutex(inode);
+ mutex_lock(aio_mutex);
+ ext4_unwritten_wait(inode);
+ }
+ if (!i_mutex_grabbed)
mutex_lock(&inode->i_mutex);
+ i_mutex_grabbed = 1;
+
+ if (o_direct) {
if (aio_mutex)
mutex_unlock(aio_mutex);
blk_start_plug(&plug);
@@ -170,11 +179,11 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
overwrite = 1;
}
- } else
- mutex_lock(&inode->i_mutex);
+ }
ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
mutex_unlock(&inode->i_mutex);
+ i_mutex_grabbed = 0;
if (ret > 0) {
ssize_t err;
@@ -186,6 +195,9 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
if (o_direct)
blk_finish_plug(&plug);
+errout:
+ if (i_mutex_grabbed)
+ mutex_unlock(&inode->i_mutex);
return ret;
}
--
1.9.0
--
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