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btrfs: don't sleep in btrfs_encoded_read() if IOCB_NOWAIT is set

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Change btrfs_encoded_read() so that it returns -EAGAIN rather than sleeps
if IOCB_NOWAIT is set in iocb->ki_flags. The conditions that require
sleeping are: inode lock, writeback, extent lock, ordered range.

Signed-off-by: Mark Harmstone <maharmstone@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Mark Harmstone 2024-10-22 15:50:18 +01:00 committed by David Sterba
parent 26efd44796
commit 973a432637
1 changed files with 44 additions and 11 deletions
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55
fs/btrfs/inode.c
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@ -8983,12 +8983,16 @@ static ssize_t btrfs_encoded_read_inline(
unsigned long ptr;
void *tmp;
ssize_t ret;
const bool nowait = (iocb->ki_flags & IOCB_NOWAIT);
path = btrfs_alloc_path();
if (!path) {
ret = -ENOMEM;
goto out;
}
path->nowait = nowait;
ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode),
extent_start, 0);
if (ret) {
@ -9198,11 +9202,15 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
size_t count = iov_iter_count(iter);
u64 start, lockend;
struct extent_map *em;
const bool nowait = (iocb->ki_flags & IOCB_NOWAIT);
bool unlocked = false;
file_accessed(iocb->ki_filp);
btrfs_inode_lock(inode, BTRFS_ILOCK_SHARED);
ret = btrfs_inode_lock(inode,
BTRFS_ILOCK_SHARED | (nowait ? BTRFS_ILOCK_TRY : 0));
if (ret)
return ret;
if (iocb->ki_pos >= inode->vfs_inode.i_size) {
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
@ -9215,21 +9223,46 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
*/
lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;
for (;;) {
if (nowait) {
struct btrfs_ordered_extent *ordered;
ret = btrfs_wait_ordered_range(inode, start,
lockend - start + 1);
if (ret)
if (filemap_range_needs_writeback(inode->vfs_inode.i_mapping,
start, lockend)) {
ret = -EAGAIN;
goto out_unlock_inode;
lock_extent(io_tree, start, lockend, cached_state);
}
if (!try_lock_extent(io_tree, start, lockend, cached_state)) {
ret = -EAGAIN;
goto out_unlock_inode;
}
ordered = btrfs_lookup_ordered_range(inode, start,
lockend - start + 1);
if (!ordered)
break;
btrfs_put_ordered_extent(ordered);
unlock_extent(io_tree, start, lockend, cached_state);
cond_resched();
if (ordered) {
btrfs_put_ordered_extent(ordered);
unlock_extent(io_tree, start, lockend, cached_state);
ret = -EAGAIN;
goto out_unlock_inode;
}
} else {
for (;;) {
struct btrfs_ordered_extent *ordered;
ret = btrfs_wait_ordered_range(inode, start,
lockend - start + 1);
if (ret)
goto out_unlock_inode;
lock_extent(io_tree, start, lockend, cached_state);
ordered = btrfs_lookup_ordered_range(inode, start,
lockend - start + 1);
if (!ordered)
break;
btrfs_put_ordered_extent(ordered);
unlock_extent(io_tree, start, lockend, cached_state);
cond_resched();
}
}
em = btrfs_get_extent(inode, NULL, start, lockend - start + 1);