mirror of
https://github.com/torvalds/linux.git
synced 2026-05-13 00:28:54 +02:00
Linux kernel source tree
be049c3a08
When writing back an inode and performing an fsync on it concurrently, a
deadlock issue may arise as shown below. In each writeback iteration, a
clean inode is requeued to the wb->b_dirty queue due to non-zero
pages_skipped, without anything actually being written. This causes an
infinite loop and prevents the plug from being flushed, resulting in a
deadlock. We now avoid requeuing the clean inode to prevent this issue.
wb_writeback fsync (inode-Y)
blk_start_plug(&plug)
for (;;) {
iter i-1: some reqs with page-X added into plug->mq_list // f2fs node page-X with PG_writeback
filemap_fdatawrite
__filemap_fdatawrite_range // write inode-Y with sync_mode WB_SYNC_ALL
do_writepages
f2fs_write_data_pages
__f2fs_write_data_pages // wb_sync_req[DATA]++ for WB_SYNC_ALL
f2fs_write_cache_pages
f2fs_write_single_data_page
f2fs_do_write_data_page
f2fs_outplace_write_data
f2fs_update_data_blkaddr
f2fs_wait_on_page_writeback
wait_on_page_writeback // wait for f2fs node page-X
iter i:
progress = __writeback_inodes_wb(wb, work)
. writeback_sb_inodes
. __writeback_single_inode // write inode-Y with sync_mode WB_SYNC_NONE
. . do_writepages
. . f2fs_write_data_pages
. . . __f2fs_write_data_pages // skip writepages due to (wb_sync_req[DATA]>0)
. . . wbc->pages_skipped += get_dirty_pages(inode) // wbc->pages_skipped = 1
. if (!(inode->i_state & I_DIRTY_ALL)) // i_state = I_SYNC | I_SYNC_QUEUED
. total_wrote++; // total_wrote = 1
. requeue_inode // requeue inode-Y to wb->b_dirty queue due to non-zero pages_skipped
if (progress) // progress = 1
continue;
iter i+1:
queue_io
// similar process with iter i, infinite for-loop !
}
blk_finish_plug(&plug) // flush plug won't be called
Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230916045131.957929-1-guochunhai@vivo.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.