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Date: Mon, 3 Apr 2017 13:53:05 -0500
From: Goldwyn Rodrigues <rgoldwyn@...e.de>
To: linux-fsdevel@...r.kernel.org
Cc: jack@...e.com, hch@...radead.org, linux-block@...r.kernel.org,
linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org, sagi@...mberg.me, avi@...lladb.com,
axboe@...nel.dk, linux-api@...r.kernel.org, willy@...radead.org,
tom.leiming@...il.com, Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: [PATCH 6/8] nowait aio: ext4
From: Goldwyn Rodrigues <rgoldwyn@...e.com>
Return EAGAIN if any of the following checks fail for direct I/O:
+ i_rwsem is lockable
+ Writing beyond end of file (will trigger allocation)
+ Blocks are not allocated at the write location
---
fs/ext4/file.c | 48 +++++++++++++++++++++++++++++++-----------------
fs/ext4/super.c | 6 +++---
2 files changed, 34 insertions(+), 20 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 8210c1f..e223b9f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -127,27 +127,22 @@ ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
return 0;
}
-/* Is IO overwriting allocated and initialized blocks? */
-static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
+/* Are IO blocks allocated */
+static bool ext4_blocks_mapped(struct inode *inode, loff_t pos, loff_t len,
+ struct ext4_map_blocks *map)
{
- struct ext4_map_blocks map;
unsigned int blkbits = inode->i_blkbits;
int err, blklen;
if (pos + len > i_size_read(inode))
return false;
- map.m_lblk = pos >> blkbits;
- map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
- blklen = map.m_len;
+ map->m_lblk = pos >> blkbits;
+ map->m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
+ blklen = map->m_len;
- err = ext4_map_blocks(NULL, inode, &map, 0);
- /*
- * 'err==len' means that all of the blocks have been preallocated,
- * regardless of whether they have been initialized or not. To exclude
- * unwritten extents, we need to check m_flags.
- */
- return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
+ err = ext4_map_blocks(NULL, inode, map, 0);
+ return err == blklen;
}
static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
@@ -204,6 +199,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
int o_direct = iocb->ki_flags & IOCB_DIRECT;
+ int nowait = iocb->ki_flags & IOCB_NOWAIT;
int unaligned_aio = 0;
int overwrite = 0;
ssize_t ret;
@@ -216,7 +212,13 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
return ext4_dax_write_iter(iocb, from);
#endif
- inode_lock(inode);
+ if (o_direct && nowait) {
+ if (!inode_trylock(inode))
+ return -EAGAIN;
+ } else {
+ inode_lock(inode);
+ }
+
ret = ext4_write_checks(iocb, from);
if (ret <= 0)
goto out;
@@ -235,9 +237,21 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
iocb->private = &overwrite;
/* Check whether we do a DIO overwrite or not */
- if (o_direct && ext4_should_dioread_nolock(inode) && !unaligned_aio &&
- ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from)))
- overwrite = 1;
+ if (o_direct && !unaligned_aio) {
+ struct ext4_map_blocks map;
+ if (ext4_blocks_mapped(inode, iocb->ki_pos,
+ iov_iter_count(from), &map)) {
+ /* To exclude unwritten extents, we need to check
+ * m_flags.
+ */
+ if (ext4_should_dioread_nolock(inode) &&
+ (map.m_flags & EXT4_MAP_MAPPED))
+ overwrite = 1;
+ } else if (iocb->ki_flags & IOCB_NOWAIT) {
+ ret = -EAGAIN;
+ goto out;
+ }
+ }
ret = __generic_file_write_iter(iocb, from);
inode_unlock(inode);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a9448db..e1d424a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -117,7 +117,7 @@ static struct file_system_type ext2_fs_type = {
.name = "ext2",
.mount = ext4_mount,
.kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV,
+ .fs_flags = FS_REQUIRES_DEV | FS_NOWAIT,
};
MODULE_ALIAS_FS("ext2");
MODULE_ALIAS("ext2");
@@ -132,7 +132,7 @@ static struct file_system_type ext3_fs_type = {
.name = "ext3",
.mount = ext4_mount,
.kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV,
+ .fs_flags = FS_REQUIRES_DEV | FS_NOWAIT,
};
MODULE_ALIAS_FS("ext3");
MODULE_ALIAS("ext3");
@@ -5623,7 +5623,7 @@ static struct file_system_type ext4_fs_type = {
.name = "ext4",
.mount = ext4_mount,
.kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV,
+ .fs_flags = FS_REQUIRES_DEV | FS_NOWAIT,
};
MODULE_ALIAS_FS("ext4");
--
2.10.2
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