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btrfs: change btrfs_encoded_read() so that reading of extent is done …
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…by caller

Change the behaviour of btrfs_encoded_read() so that if it needs to read
an extent from disk, it leaves the extent and inode locked and returns
-EIOCBQUEUED. The caller is then responsible for doing the I/O via
btrfs_encoded_read_regular() and unlocking the extent and inode.

Signed-off-by: Mark Harmstone <maharmstone@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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@maharmstone @kdave
maharmstone authored and kdave committed Nov 11, 2024
1 parent 4bca741 commit 26efd44
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Showing 3 changed files with 66 additions and 32 deletions.
9 changes: 8 additions & 1 deletion fs/btrfs/btrfs_inode.h
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Original file line number Diff line number Diff line change
Expand Up @@ -615,7 +615,14 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
u64 disk_bytenr, u64 disk_io_size,
struct page **pages);
ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
struct btrfs_ioctl_encoded_io_args *encoded);
struct btrfs_ioctl_encoded_io_args *encoded,
struct extent_state **cached_state,
u64 *disk_bytenr, u64 *disk_io_size);
ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,
u64 start, u64 lockend,
struct extent_state **cached_state,
u64 disk_bytenr, u64 disk_io_size,
size_t count, bool compressed, bool *unlocked);
ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
const struct btrfs_ioctl_encoded_io_args *encoded);

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57 changes: 27 additions & 30 deletions fs/btrfs/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9122,13 +9122,11 @@ int btrfs_encoded_read_regular_fill_pages(struct btrfs_inode *inode,
return blk_status_to_errno(READ_ONCE(priv.status));
}

static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb,
struct iov_iter *iter,
u64 start, u64 lockend,
struct extent_state **cached_state,
u64 disk_bytenr, u64 disk_io_size,
size_t count, bool compressed,
bool *unlocked)
ssize_t btrfs_encoded_read_regular(struct kiocb *iocb, struct iov_iter *iter,
u64 start, u64 lockend,
struct extent_state **cached_state,
u64 disk_bytenr, u64 disk_io_size,
size_t count, bool compressed, bool *unlocked)
{
struct btrfs_inode *inode = BTRFS_I(file_inode(iocb->ki_filp));
struct extent_io_tree *io_tree = &inode->io_tree;
Expand Down Expand Up @@ -9189,15 +9187,16 @@ static ssize_t btrfs_encoded_read_regular(struct kiocb *iocb,
}

ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
struct btrfs_ioctl_encoded_io_args *encoded)
struct btrfs_ioctl_encoded_io_args *encoded,
struct extent_state **cached_state,
u64 *disk_bytenr, u64 *disk_io_size)
{
struct btrfs_inode *inode = BTRFS_I(file_inode(iocb->ki_filp));
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct extent_io_tree *io_tree = &inode->io_tree;
ssize_t ret;
size_t count = iov_iter_count(iter);
u64 start, lockend, disk_bytenr, disk_io_size;
struct extent_state *cached_state = NULL;
u64 start, lockend;
struct extent_map *em;
bool unlocked = false;

Expand All @@ -9223,13 +9222,13 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
lockend - start + 1);
if (ret)
goto out_unlock_inode;
lock_extent(io_tree, start, lockend, &cached_state);
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);
unlock_extent(io_tree, start, lockend, cached_state);
cond_resched();
}

Expand All @@ -9249,7 +9248,7 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
free_extent_map(em);
em = NULL;
ret = btrfs_encoded_read_inline(iocb, iter, start, lockend,
&cached_state, extent_start,
cached_state, extent_start,
count, encoded, &unlocked);
goto out_em;
}
Expand All @@ -9262,12 +9261,12 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
inode->vfs_inode.i_size) - iocb->ki_pos;
if (em->disk_bytenr == EXTENT_MAP_HOLE ||
(em->flags & EXTENT_FLAG_PREALLOC)) {
disk_bytenr = EXTENT_MAP_HOLE;
*disk_bytenr = EXTENT_MAP_HOLE;
count = min_t(u64, count, encoded->len);
encoded->len = count;
encoded->unencoded_len = count;
} else if (extent_map_is_compressed(em)) {
disk_bytenr = em->disk_bytenr;
*disk_bytenr = em->disk_bytenr;
/*
* Bail if the buffer isn't large enough to return the whole
* compressed extent.
Expand All @@ -9276,7 +9275,7 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
ret = -ENOBUFS;
goto out_em;
}
disk_io_size = em->disk_num_bytes;
*disk_io_size = em->disk_num_bytes;
count = em->disk_num_bytes;
encoded->unencoded_len = em->ram_bytes;
encoded->unencoded_offset = iocb->ki_pos - (em->start - em->offset);
Expand All @@ -9286,44 +9285,42 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
goto out_em;
encoded->compression = ret;
} else {
disk_bytenr = extent_map_block_start(em) + (start - em->start);
*disk_bytenr = extent_map_block_start(em) + (start - em->start);
if (encoded->len > count)
encoded->len = count;
/*
* Don't read beyond what we locked. This also limits the page
* allocations that we'll do.
*/
disk_io_size = min(lockend + 1, iocb->ki_pos + encoded->len) - start;
count = start + disk_io_size - iocb->ki_pos;
*disk_io_size = min(lockend + 1, iocb->ki_pos + encoded->len) - start;
count = start + *disk_io_size - iocb->ki_pos;
encoded->len = count;
encoded->unencoded_len = count;
disk_io_size = ALIGN(disk_io_size, fs_info->sectorsize);
*disk_io_size = ALIGN(*disk_io_size, fs_info->sectorsize);
}
free_extent_map(em);
em = NULL;

if (disk_bytenr == EXTENT_MAP_HOLE) {
unlock_extent(io_tree, start, lockend, &cached_state);
if (*disk_bytenr == EXTENT_MAP_HOLE) {
unlock_extent(io_tree, start, lockend, cached_state);
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
unlocked = true;
ret = iov_iter_zero(count, iter);
if (ret != count)
ret = -EFAULT;
} else {
ret = btrfs_encoded_read_regular(iocb, iter, start, lockend,
&cached_state, disk_bytenr,
disk_io_size, count,
encoded->compression,
&unlocked);
ret = -EIOCBQUEUED;
goto out_em;
}

out_em:
free_extent_map(em);
out_unlock_extent:
if (!unlocked)
unlock_extent(io_tree, start, lockend, &cached_state);
/* Leave inode and extent locked if we need to do a read. */
if (!unlocked && ret != -EIOCBQUEUED)
unlock_extent(io_tree, start, lockend, cached_state);
out_unlock_inode:
if (!unlocked)
if (!unlocked && ret != -EIOCBQUEUED)
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
return ret;
}
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32 changes: 31 additions & 1 deletion fs/btrfs/ioctl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4513,12 +4513,17 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
size_t copy_end_kernel = offsetofend(struct btrfs_ioctl_encoded_io_args,
flags);
size_t copy_end;
struct btrfs_inode *inode = BTRFS_I(file_inode(file));
struct btrfs_fs_info *fs_info = inode->root->fs_info;
struct extent_io_tree *io_tree = &inode->io_tree;
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
struct iov_iter iter;
loff_t pos;
struct kiocb kiocb;
ssize_t ret;
u64 disk_bytenr, disk_io_size;
struct extent_state *cached_state = NULL;

if (!capable(CAP_SYS_ADMIN)) {
ret = -EPERM;
Expand Down Expand Up @@ -4571,7 +4576,32 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
init_sync_kiocb(&kiocb, file);
kiocb.ki_pos = pos;

ret = btrfs_encoded_read(&kiocb, &iter, &args);
ret = btrfs_encoded_read(&kiocb, &iter, &args, &cached_state,
&disk_bytenr, &disk_io_size);

if (ret == -EIOCBQUEUED) {
bool unlocked = false;
u64 start, lockend, count;

start = ALIGN_DOWN(kiocb.ki_pos, fs_info->sectorsize);
lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;

if (args.compression)
count = disk_io_size;
else
count = args.len;

ret = btrfs_encoded_read_regular(&kiocb, &iter, start, lockend,
&cached_state, disk_bytenr,
disk_io_size, count,
args.compression, &unlocked);

if (!unlocked) {
unlock_extent(io_tree, start, lockend, &cached_state);
btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
}
}

if (ret >= 0) {
fsnotify_access(file);
if (copy_to_user(argp + copy_end,
Expand Down

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