3.16.70-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hou Tao <houtao1@xxxxxxxxxx> commit 5e3cc1ee1405a7eb3487ed24f786dec01b4cbe1f upstream. Use inode->i_lock to protect i_size_write(), else i_size_read() in generic_fillattr() may loop infinitely in read_seqcount_begin() when multiple processes invoke v9fs_vfs_getattr() or v9fs_vfs_getattr_dotl() simultaneously under 32-bit SMP environment, and a soft lockup will be triggered as show below: watchdog: BUG: soft lockup - CPU#5 stuck for 22s! [stat:2217] Modules linked in: CPU: 5 PID: 2217 Comm: stat Not tainted 5.0.0-rc1-00005-g7f702faf5a9e #4 Hardware name: Generic DT based system PC is at generic_fillattr+0x104/0x108 LR is at 0xec497f00 pc : [<802b8898>] lr : [<ec497f00>] psr: 200c0013 sp : ec497e20 ip : ed608030 fp : ec497e3c r10: 00000000 r9 : ec497f00 r8 : ed608030 r7 : ec497ebc r6 : ec497f00 r5 : ee5c1550 r4 : ee005780 r3 : 0000052d r2 : 00000000 r1 : ec497f00 r0 : ed608030 Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: ac48006a DAC: 00000051 CPU: 5 PID: 2217 Comm: stat Not tainted 5.0.0-rc1-00005-g7f702faf5a9e #4 Hardware name: Generic DT based system Backtrace: [<8010d974>] (dump_backtrace) from [<8010dc88>] (show_stack+0x20/0x24) [<8010dc68>] (show_stack) from [<80a1d194>] (dump_stack+0xb0/0xdc) [<80a1d0e4>] (dump_stack) from [<80109f34>] (show_regs+0x1c/0x20) [<80109f18>] (show_regs) from [<801d0a80>] (watchdog_timer_fn+0x280/0x2f8) [<801d0800>] (watchdog_timer_fn) from [<80198658>] (__hrtimer_run_queues+0x18c/0x380) [<801984cc>] (__hrtimer_run_queues) from [<80198e60>] (hrtimer_run_queues+0xb8/0xf0) [<80198da8>] (hrtimer_run_queues) from [<801973e8>] (run_local_timers+0x28/0x64) [<801973c0>] (run_local_timers) from [<80197460>] (update_process_times+0x3c/0x6c) [<80197424>] (update_process_times) from [<801ab2b8>] (tick_nohz_handler+0xe0/0x1bc) [<801ab1d8>] (tick_nohz_handler) from [<80843050>] (arch_timer_handler_virt+0x38/0x48) [<80843018>] (arch_timer_handler_virt) from [<80180a64>] (handle_percpu_devid_irq+0x8c/0x240) [<801809d8>] (handle_percpu_devid_irq) from [<8017ac20>] (generic_handle_irq+0x34/0x44) [<8017abec>] (generic_handle_irq) from [<8017b344>] (__handle_domain_irq+0x6c/0xc4) [<8017b2d8>] (__handle_domain_irq) from [<801022e0>] (gic_handle_irq+0x4c/0x88) [<80102294>] (gic_handle_irq) from [<80101a30>] (__irq_svc+0x70/0x98) [<802b8794>] (generic_fillattr) from [<8056b284>] (v9fs_vfs_getattr_dotl+0x74/0xa4) [<8056b210>] (v9fs_vfs_getattr_dotl) from [<802b8904>] (vfs_getattr_nosec+0x68/0x7c) [<802b889c>] (vfs_getattr_nosec) from [<802b895c>] (vfs_getattr+0x44/0x48) [<802b8918>] (vfs_getattr) from [<802b8a74>] (vfs_statx+0x9c/0xec) [<802b89d8>] (vfs_statx) from [<802b9428>] (sys_lstat64+0x48/0x78) [<802b93e0>] (sys_lstat64) from [<80101000>] (ret_fast_syscall+0x0/0x28) [dominique.martinet@xxxxxx: updated comment to not refer to a function in another subsystem] Link: http://lkml.kernel.org/r/20190124063514.8571-2-houtao1@xxxxxxxxxx Fixes: 7549ae3e81cc ("9p: Use the i_size_[read, write]() macros instead of using inode->i_size directly.") Reported-by: Xing Gaopeng <xingaopeng@xxxxxxxxxx> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> Signed-off-by: Dominique Martinet <dominique.martinet@xxxxxx> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- fs/9p/v9fs_vfs.h | 23 +++++++++++++++++++++-- fs/9p/vfs_file.c | 6 +++++- fs/9p/vfs_inode.c | 23 +++++++++++------------ fs/9p/vfs_inode_dotl.c | 27 ++++++++++++++------------- fs/9p/vfs_super.c | 4 ++-- 5 files changed, 53 insertions(+), 30 deletions(-) --- a/fs/9p/v9fs_vfs.h +++ b/fs/9p/v9fs_vfs.h @@ -40,6 +40,9 @@ */ #define P9_LOCK_TIMEOUT (30*HZ) +/* flags for v9fs_stat2inode() & v9fs_stat2inode_dotl() */ +#define V9FS_STAT2INODE_KEEP_ISIZE 1 + extern struct file_system_type v9fs_fs_type; extern const struct address_space_operations v9fs_addr_operations; extern const struct file_operations v9fs_file_operations; @@ -61,8 +64,10 @@ int v9fs_init_inode(struct v9fs_session_ struct inode *inode, umode_t mode, dev_t); void v9fs_evict_inode(struct inode *inode); ino_t v9fs_qid2ino(struct p9_qid *qid); -void v9fs_stat2inode(struct p9_wstat *, struct inode *, struct super_block *); -void v9fs_stat2inode_dotl(struct p9_stat_dotl *, struct inode *); +void v9fs_stat2inode(struct p9_wstat *stat, struct inode *inode, + struct super_block *sb, unsigned int flags); +void v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode, + unsigned int flags); int v9fs_dir_release(struct inode *inode, struct file *filp); int v9fs_file_open(struct inode *inode, struct file *file); void v9fs_inode2stat(struct inode *inode, struct p9_wstat *stat); @@ -87,4 +92,18 @@ static inline void v9fs_invalidate_inode } int v9fs_open_to_dotl_flags(int flags); + +static inline void v9fs_i_size_write(struct inode *inode, loff_t i_size) +{ + /* + * 32-bit need the lock, concurrent updates could break the + * sequences and make i_size_read() loop forever. + * 64-bit updates are atomic and can skip the locking. + */ + if (sizeof(i_size) > sizeof(long)) + spin_lock(&inode->i_lock); + i_size_write(inode, i_size); + if (sizeof(i_size) > sizeof(long)) + spin_unlock(&inode->i_lock); +} #endif --- a/fs/9p/vfs_file.c +++ b/fs/9p/vfs_file.c @@ -484,7 +484,11 @@ v9fs_file_write_internal(struct inode *i i_size = i_size_read(inode); if (*offset > i_size) { inode_add_bytes(inode, *offset - i_size); - i_size_write(inode, *offset); + /* + * Need to serialize against i_size_write() in + * v9fs_stat2inode() + */ + v9fs_i_size_write(inode, *offset); } } if (n < 0) --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -538,7 +538,7 @@ static struct inode *v9fs_qid_iget(struc if (retval) goto error; - v9fs_stat2inode(st, inode, sb); + v9fs_stat2inode(st, inode, sb, 0); v9fs_cache_inode_get_cookie(inode); unlock_new_inode(inode); return inode; @@ -1074,7 +1074,7 @@ v9fs_vfs_getattr(struct vfsmount *mnt, s if (IS_ERR(st)) return PTR_ERR(st); - v9fs_stat2inode(st, dentry->d_inode, dentry->d_inode->i_sb); + v9fs_stat2inode(st, dentry->d_inode, dentry->d_inode->i_sb, 0); generic_fillattr(dentry->d_inode, stat); p9stat_free(st); @@ -1152,12 +1152,13 @@ static int v9fs_vfs_setattr(struct dentr * @stat: Plan 9 metadata (mistat) structure * @inode: inode to populate * @sb: superblock of filesystem + * @flags: control flags (e.g. V9FS_STAT2INODE_KEEP_ISIZE) * */ void v9fs_stat2inode(struct p9_wstat *stat, struct inode *inode, - struct super_block *sb) + struct super_block *sb, unsigned int flags) { umode_t mode; char ext[32]; @@ -1198,10 +1199,11 @@ v9fs_stat2inode(struct p9_wstat *stat, s mode = p9mode2perm(v9ses, stat); mode |= inode->i_mode & ~S_IALLUGO; inode->i_mode = mode; - i_size_write(inode, stat->length); + if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE)) + v9fs_i_size_write(inode, stat->length); /* not real number of blocks, but 512 byte ones ... */ - inode->i_blocks = (i_size_read(inode) + 512 - 1) >> 9; + inode->i_blocks = (stat->length + 512 - 1) >> 9; v9inode->cache_validity &= ~V9FS_INO_INVALID_ATTR; } @@ -1465,9 +1467,9 @@ int v9fs_refresh_inode(struct p9_fid *fi { int umode; dev_t rdev; - loff_t i_size; struct p9_wstat *st; struct v9fs_session_info *v9ses; + unsigned int flags; v9ses = v9fs_inode2v9ses(inode); st = p9_client_stat(fid); @@ -1480,16 +1482,13 @@ int v9fs_refresh_inode(struct p9_fid *fi if ((inode->i_mode & S_IFMT) != (umode & S_IFMT)) goto out; - spin_lock(&inode->i_lock); /* * We don't want to refresh inode->i_size, * because we may have cached data */ - i_size = inode->i_size; - v9fs_stat2inode(st, inode, inode->i_sb); - if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) - inode->i_size = i_size; - spin_unlock(&inode->i_lock); + flags = (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) ? + V9FS_STAT2INODE_KEEP_ISIZE : 0; + v9fs_stat2inode(st, inode, inode->i_sb, flags); out: p9stat_free(st); kfree(st); --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -143,7 +143,7 @@ static struct inode *v9fs_qid_iget_dotl( if (retval) goto error; - v9fs_stat2inode_dotl(st, inode); + v9fs_stat2inode_dotl(st, inode, 0); v9fs_cache_inode_get_cookie(inode); retval = v9fs_get_acl(inode, fid); if (retval) @@ -498,7 +498,7 @@ v9fs_vfs_getattr_dotl(struct vfsmount *m if (IS_ERR(st)) return PTR_ERR(st); - v9fs_stat2inode_dotl(st, dentry->d_inode); + v9fs_stat2inode_dotl(st, dentry->d_inode, 0); generic_fillattr(dentry->d_inode, stat); /* Change block size to what the server returned */ stat->blksize = st->st_blksize; @@ -609,11 +609,13 @@ int v9fs_vfs_setattr_dotl(struct dentry * v9fs_stat2inode_dotl - populate an inode structure with stat info * @stat: stat structure * @inode: inode to populate + * @flags: ctrl flags (e.g. V9FS_STAT2INODE_KEEP_ISIZE) * */ void -v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode) +v9fs_stat2inode_dotl(struct p9_stat_dotl *stat, struct inode *inode, + unsigned int flags) { umode_t mode; struct v9fs_inode *v9inode = V9FS_I(inode); @@ -633,7 +635,8 @@ v9fs_stat2inode_dotl(struct p9_stat_dotl mode |= inode->i_mode & ~S_IALLUGO; inode->i_mode = mode; - i_size_write(inode, stat->st_size); + if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE)) + v9fs_i_size_write(inode, stat->st_size); inode->i_blocks = stat->st_blocks; } else { if (stat->st_result_mask & P9_STATS_ATIME) { @@ -663,8 +666,9 @@ v9fs_stat2inode_dotl(struct p9_stat_dotl } if (stat->st_result_mask & P9_STATS_RDEV) inode->i_rdev = new_decode_dev(stat->st_rdev); - if (stat->st_result_mask & P9_STATS_SIZE) - i_size_write(inode, stat->st_size); + if (!(flags & V9FS_STAT2INODE_KEEP_ISIZE) && + stat->st_result_mask & P9_STATS_SIZE) + v9fs_i_size_write(inode, stat->st_size); if (stat->st_result_mask & P9_STATS_BLOCKS) inode->i_blocks = stat->st_blocks; } @@ -946,9 +950,9 @@ ndset: int v9fs_refresh_inode_dotl(struct p9_fid *fid, struct inode *inode) { - loff_t i_size; struct p9_stat_dotl *st; struct v9fs_session_info *v9ses; + unsigned int flags; v9ses = v9fs_inode2v9ses(inode); st = p9_client_getattr_dotl(fid, P9_STATS_ALL); @@ -960,16 +964,13 @@ int v9fs_refresh_inode_dotl(struct p9_fi if ((inode->i_mode & S_IFMT) != (st->st_mode & S_IFMT)) goto out; - spin_lock(&inode->i_lock); /* * We don't want to refresh inode->i_size, * because we may have cached data */ - i_size = inode->i_size; - v9fs_stat2inode_dotl(st, inode); - if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) - inode->i_size = i_size; - spin_unlock(&inode->i_lock); + flags = (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) ? + V9FS_STAT2INODE_KEEP_ISIZE : 0; + v9fs_stat2inode_dotl(st, inode, flags); out: kfree(st); return 0; --- a/fs/9p/vfs_super.c +++ b/fs/9p/vfs_super.c @@ -169,7 +169,7 @@ static struct dentry *v9fs_mount(struct goto release_sb; } root->d_inode->i_ino = v9fs_qid2ino(&st->qid); - v9fs_stat2inode_dotl(st, root->d_inode); + v9fs_stat2inode_dotl(st, root->d_inode, 0); kfree(st); } else { struct p9_wstat *st = NULL; @@ -180,7 +180,7 @@ static struct dentry *v9fs_mount(struct } root->d_inode->i_ino = v9fs_qid2ino(&st->qid); - v9fs_stat2inode(st, root->d_inode, sb); + v9fs_stat2inode(st, root->d_inode, sb, 0); p9stat_free(st); kfree(st);
