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authorAl Viro <viro@zeniv.linux.org.uk>2017-06-15 00:17:30 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2017-06-15 00:41:18 -0400
commit09bf4f5b6e6013f0ad6b090d4a8deebd4e56d878 (patch)
tree9fdf602d8c5ce36c60e12f3363658882b138c15f /fs/ufs
parent267309f394bf3cd8db001992890b1fa52b97974e (diff)
downloadlinux-stericsson-09bf4f5b6e6013f0ad6b090d4a8deebd4e56d878.tar.gz
ufs: avoid grabbing ->truncate_mutex if possible
tail unpacking is done in a wrong place; the deadlocks galore is best dealt with by doing that in ->write_iter() (and switching to iomap, while we are at it), but that's rather painful to backport. The trouble comes from grabbing pages that cover the beginning of tail from inside of ufs_new_fragments(); ongoing pageout of any of those is going to deadlock on ->truncate_mutex with process that got around to extending the tail holding that and waiting for page to get unlocked, while ->writepage() on that page is waiting on ->truncate_mutex. The thing is, we don't need ->truncate_mutex when the fragment we are trying to map is within the tail - the damn thing is allocated (tail can't contain holes). Let's do a plain lookup and if the fragment is present, we can just pretend that we'd won the race in almost all cases. The only exception is a fragment between the end of tail and the end of block containing tail. Protect ->i_lastfrag with ->meta_lock - read_seqlock_excl() is sufficient. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/ufs')
-rw-r--r--fs/ufs/balloc.c10
-rw-r--r--fs/ufs/inode.c26
2 files changed, 26 insertions, 10 deletions
diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index af0473a851af..d56d9bc705fe 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -423,12 +423,12 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
if (result) {
ufs_clear_frags(inode, result + oldcount,
newcount - oldcount, locked_page != NULL);
+ *err = 0;
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_cpu_to_data_ptr(sb, p, result);
- write_sequnlock(&UFS_I(inode)->meta_lock);
- *err = 0;
UFS_I(inode)->i_lastfrag =
max(UFS_I(inode)->i_lastfrag, fragment + count);
+ write_sequnlock(&UFS_I(inode)->meta_lock);
}
mutex_unlock(&UFS_SB(sb)->s_lock);
UFSD("EXIT, result %llu\n", (unsigned long long)result);
@@ -441,8 +441,10 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
result = ufs_add_fragments(inode, tmp, oldcount, newcount);
if (result) {
*err = 0;
+ read_seqlock_excl(&UFS_I(inode)->meta_lock);
UFS_I(inode)->i_lastfrag = max(UFS_I(inode)->i_lastfrag,
fragment + count);
+ read_sequnlock_excl(&UFS_I(inode)->meta_lock);
ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
locked_page != NULL);
mutex_unlock(&UFS_SB(sb)->s_lock);
@@ -479,12 +481,12 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
ufs_change_blocknr(inode, fragment - oldcount, oldcount,
uspi->s_sbbase + tmp,
uspi->s_sbbase + result, locked_page);
+ *err = 0;
write_seqlock(&UFS_I(inode)->meta_lock);
ufs_cpu_to_data_ptr(sb, p, result);
- write_sequnlock(&UFS_I(inode)->meta_lock);
- *err = 0;
UFS_I(inode)->i_lastfrag = max(UFS_I(inode)->i_lastfrag,
fragment + count);
+ write_sequnlock(&UFS_I(inode)->meta_lock);
mutex_unlock(&UFS_SB(sb)->s_lock);
if (newcount < request)
ufs_free_fragments (inode, result + newcount, request - newcount);
diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c
index da553ffec85b..1dda6c4875f9 100644
--- a/fs/ufs/inode.c
+++ b/fs/ufs/inode.c
@@ -401,13 +401,20 @@ static int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buff
u64 phys64 = 0;
unsigned frag = fragment & uspi->s_fpbmask;
- if (!create) {
- phys64 = ufs_frag_map(inode, offsets, depth);
- if (phys64)
- map_bh(bh_result, sb, phys64 + frag);
- return 0;
- }
+ phys64 = ufs_frag_map(inode, offsets, depth);
+ if (!create)
+ goto done;
+ if (phys64) {
+ if (fragment >= UFS_NDIR_FRAGMENT)
+ goto done;
+ read_seqlock_excl(&UFS_I(inode)->meta_lock);
+ if (fragment < UFS_I(inode)->i_lastfrag) {
+ read_sequnlock_excl(&UFS_I(inode)->meta_lock);
+ goto done;
+ }
+ read_sequnlock_excl(&UFS_I(inode)->meta_lock);
+ }
/* This code entered only while writing ....? */
mutex_lock(&UFS_I(inode)->truncate_mutex);
@@ -451,6 +458,11 @@ out:
}
mutex_unlock(&UFS_I(inode)->truncate_mutex);
return err;
+
+done:
+ if (phys64)
+ map_bh(bh_result, sb, phys64 + frag);
+ return 0;
}
static int ufs_writepage(struct page *page, struct writeback_control *wbc)
@@ -1161,7 +1173,9 @@ static void ufs_truncate_blocks(struct inode *inode)
free_full_branch(inode, block, i - UFS_IND_BLOCK + 1);
}
}
+ read_seqlock_excl(&ufsi->meta_lock);
ufsi->i_lastfrag = DIRECT_FRAGMENT;
+ read_sequnlock_excl(&ufsi->meta_lock);
mark_inode_dirty(inode);
mutex_unlock(&ufsi->truncate_mutex);
}