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Message-ID: <20130111201211.GA20981@quack.suse.cz> Date: Fri, 11 Jan 2013 21:12:11 +0100 From: Jan Kara <jack@...e.cz> To: Miao Xie <miaox@...fujitsu.com> Cc: Linux Fsdevel <linux-fsdevel@...r.kernel.org>, Linux Btrfs <linux-btrfs@...r.kernel.org>, Linux Ext4 <linux-ext4@...r.kernel.org>, Linux Kernel <linux-kernel@...r.kernel.org>, dsterba@...e.cz, Christoph Hellwig <hch@...radead.org>, Kamal Mostafa <kamal@...onical.com>, Al Viro <viro@...IV.linux.org.uk>, Wu Fengguang <fengguang.wu@...el.com> Subject: Re: [PATCH V2] vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename them On Thu 10-01-13 13:47:57, Miao Xie wrote: > writeback_inodes_sb(_nr)_if_idle() is re-implemented by replacing down_read() > with down_read_trylock() because > - If ->s_umount is write locked, then the sb is not idle. That is > writeback_inodes_sb(_nr)_if_idle() needn't wait for the lock. > - writeback_inodes_sb(_nr)_if_idle() grabs s_umount lock when it want to start > writeback, it may bring us deadlock problem when doing umount. In order to > fix the problem, ext4 and btrfs implemented their own writeback functions > instead of writeback_inodes_sb(_nr)_if_idle(), but it introduced the redundant > code, it is better to implement a new writeback_inodes_sb(_nr)_if_idle(). > > The name of these two functions is cumbersome, so rename them to > try_to_writeback_inodes_sb(_nr). > > This idea came from Christoph Hellwig. > Some code is from the patch of Kamal Mostafa. The patch looks good. Thanks! You can add: Reviewed-by: Jan Kara <jack@...e.cz> BTW, since changes to filesystems are minimal, maybe Fengguang can take the patch through his writeback tree? Fengguang? Honza > > Signed-off-by: Miao Xie <miaox@...fujitsu.com> > --- > Changelog v1 -> v2: > - do not remove EXPORT_SYMBOL of writeback_inodes_sb_br() > --- > fs/btrfs/extent-tree.c | 20 +++----------------- > fs/ext4/inode.c | 8 ++------ > fs/fs-writeback.c | 44 ++++++++++++++++++++------------------------ > include/linux/writeback.h | 6 +++--- > 4 files changed, 28 insertions(+), 50 deletions(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 521e9d4..f31abb1 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -3689,20 +3689,6 @@ static int can_overcommit(struct btrfs_root *root, > return 0; > } > > -static int writeback_inodes_sb_nr_if_idle_safe(struct super_block *sb, > - unsigned long nr_pages, > - enum wb_reason reason) > -{ > - if (!writeback_in_progress(sb->s_bdi) && > - down_read_trylock(&sb->s_umount)) { > - writeback_inodes_sb_nr(sb, nr_pages, reason); > - up_read(&sb->s_umount); > - return 1; > - } > - > - return 0; > -} > - > /* > * shrink metadata reservation for delalloc > */ > @@ -3735,9 +3721,9 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig, > while (delalloc_bytes && loops < 3) { > max_reclaim = min(delalloc_bytes, to_reclaim); > nr_pages = max_reclaim >> PAGE_CACHE_SHIFT; > - writeback_inodes_sb_nr_if_idle_safe(root->fs_info->sb, > - nr_pages, > - WB_REASON_FS_FREE_SPACE); > + try_to_writeback_inodes_sb_nr(root->fs_info->sb, > + nr_pages, > + WB_REASON_FS_FREE_SPACE); > > /* > * We need to wait for the async pages to actually start before > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index cbfe13b..5f6eef7 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -2512,12 +2512,8 @@ static int ext4_nonda_switch(struct super_block *sb) > /* > * Start pushing delalloc when 1/2 of free blocks are dirty. > */ > - if (dirty_blocks && (free_blocks < 2 * dirty_blocks) && > - !writeback_in_progress(sb->s_bdi) && > - down_read_trylock(&sb->s_umount)) { > - writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE); > - up_read(&sb->s_umount); > - } > + if (dirty_blocks && (free_blocks < 2 * dirty_blocks)) > + try_to_writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE); > > if (2 * free_blocks < 3 * dirty_blocks || > free_blocks < (dirty_blocks + EXT4_FREECLUSTERS_WATERMARK)) { > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 310972b..ad3cc46 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1332,47 +1332,43 @@ void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) > EXPORT_SYMBOL(writeback_inodes_sb); > > /** > - * writeback_inodes_sb_if_idle - start writeback if none underway > + * try_to_writeback_inodes_sb_nr - try to start writeback if none underway > * @sb: the superblock > - * @reason: reason why some writeback work was initiated > + * @nr: the number of pages to write > + * @reason: the reason of writeback > * > - * Invoke writeback_inodes_sb if no writeback is currently underway. > + * Invoke writeback_inodes_sb_nr if no writeback is currently underway. > * Returns 1 if writeback was started, 0 if not. > */ > -int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason) > +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); > - writeback_inodes_sb(sb, reason); > - up_read(&sb->s_umount); > + if (writeback_in_progress(sb->s_bdi)) > return 1; > - } else > + > + if (!down_read_trylock(&sb->s_umount)) > return 0; > + > + writeback_inodes_sb_nr(sb, nr, reason); > + up_read(&sb->s_umount); > + return 1; > } > -EXPORT_SYMBOL(writeback_inodes_sb_if_idle); > +EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr); > > /** > - * writeback_inodes_sb_nr_if_idle - start writeback if none underway > + * try_to_writeback_inodes_sb - try to start writeback if none underway > * @sb: the superblock > - * @nr: the number of pages to write > * @reason: reason why some writeback work was initiated > * > - * Invoke writeback_inodes_sb if no writeback is currently underway. > + * Implement by try_to_writeback_inodes_sb_nr() > * Returns 1 if writeback was started, 0 if not. > */ > -int writeback_inodes_sb_nr_if_idle(struct super_block *sb, > - unsigned long nr, > - enum wb_reason reason) > +int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) > { > - if (!writeback_in_progress(sb->s_bdi)) { > - down_read(&sb->s_umount); > - writeback_inodes_sb_nr(sb, nr, reason); > - up_read(&sb->s_umount); > - return 1; > - } else > - return 0; > + return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason); > } > -EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle); > +EXPORT_SYMBOL(try_to_writeback_inodes_sb); > > /** > * sync_inodes_sb - sync sb inode pages > diff --git a/include/linux/writeback.h b/include/linux/writeback.h > index b82a83a..9a9367c 100644 > --- a/include/linux/writeback.h > +++ b/include/linux/writeback.h > @@ -87,9 +87,9 @@ int inode_wait(void *); > void writeback_inodes_sb(struct super_block *, enum wb_reason reason); > void writeback_inodes_sb_nr(struct super_block *, unsigned long nr, > enum wb_reason reason); > -int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason); > -int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr, > - enum wb_reason reason); > +int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason); > +int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr, > + enum wb_reason reason); > void sync_inodes_sb(struct super_block *); > long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, > enum wb_reason reason); > -- > 1.7.11.7 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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