[PATCH v2 5/7] VFS: Avoid read-write deadlock in try_to_writeback_inodes_sb
From: Kamal Mostafa <hidden>
Date: 2011-12-08 18:04:35
Also in:
linux-fsdevel, lkml
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
From: Valerie Aurora <redacted> Use trylock in try_to_writeback_inodes_sb to avoid read-write deadlocks that could be triggered by freeze. BugLink: https://bugs.launchpad.net/bugs/897421 Signed-off-by: Valerie Aurora <redacted> Cc: Kamal Mostafa <redacted> Tested-by: Peter M. Petrakis <redacted> [kamal@canonical.com: patch restructure] Signed-off-by: Kamal Mostafa <redacted> --- fs/fs-writeback.c | 13 ++++++++----- 1 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index ea89b3f..3a80f1b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c@@ -1274,8 +1274,9 @@ EXPORT_SYMBOL(writeback_inodes_sb); * try_to_writeback_inodes_sb - start writeback if none underway * @sb: the superblock * - * Invoke writeback_inodes_sb if no writeback is currently underway. - * Returns 1 if writeback was started, 0 if not. + * Invoke writeback_inodes_sb if no writeback is currently underway + * and no one else holds the s_umount lock. Returns 1 if writeback + * was started, 0 if not. */ int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) {
@@ -1288,15 +1289,17 @@ EXPORT_SYMBOL(try_to_writeback_inodes_sb); * @sb: the superblock * @nr: the number of pages to write * - * Invoke writeback_inodes_sb if no writeback is currently underway. - * Returns 1 if writeback was started, 0 if not. + * Invoke writeback_inodes_sb if no writeback is currently underway + * and no one else holds the s_umount lock. Returns 1 if writeback + * was started, 0 if not. */ int try_to_writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, enum wb_reason reason) { if (!writeback_in_progress(sb->s_bdi)) { - down_read(&sb->s_umount); + if (!down_read_trylock(&sb->s_umount)) + return 0; if (nr == 0) writeback_inodes_sb(sb, reason); else
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1.7.5.4