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authorPranith Kumar K <pkarampu@redhat.com>2013-12-11 09:33:53 +0530
committerAnand Avati <avati@redhat.com>2014-01-19 23:05:15 -0800
commit8d55c25f158921b508bff0e7f25158991913f922 (patch)
tree258500ed1f6b15d6f2f6848a5cbd883b8dc40ea2 /api/src/glfs-handleops.c
parentc2b09dc87e0763dfdff1e93a1dc6cc4c05f091bf (diff)
syncop: Change return value of syncop
Problem: We found a day-1 bug when syncop_xxx() infra is used inside a synctask with compilation optimization (CFLAGS -O2). Detailed explanation of the Root cause: We found the bug in 'gf_defrag_migrate_data' in rebalance operation: Lets look at interesting parts of the function: int gf_defrag_migrate_data (xlator_t *this, gf_defrag_info_t *defrag, loc_t *loc, dict_t *migrate_data) { ..... code section - [ Loop ] while ((ret = syncop_readdirp (this, fd, 131072, offset, NULL, &entries)) != 0) { ..... code section - [ ERRNO-1 ] (errno of readdirp is stored in readdir_operrno by a thread) /* Need to keep track of ENOENT errno, that means, there is no need to send more readdirp() */ readdir_operrno = errno; ..... code section - [ SYNCOP-1 ] (syncop_getxattr is called by a thread) ret = syncop_getxattr (this, &entry_loc, &dict, GF_XATTR_LINKINFO_KEY); code section - [ ERRNO-2] (checking for failures of syncop_getxattr(). This may not always be executed in same thread which executed [SYNCOP-1]) if (ret < 0) { if (errno != ENODATA) { loglevel = GF_LOG_ERROR; defrag->total_failures += 1; ..... } the function above could be executed by thread(t1) till [SYNCOP-1] and code from [ERRNO-2] can be executed by a different thread(t2) because of the way syncop-infra schedules the tasks. when the code is compiled with -O2 optimization this is the assembly code that is generated: [ERRNO-1] 1165 readdir_operrno = errno; <<---- errno gets expanded as *(__errno_location()) 0x00007fd149d48b60 <+496>: callq 0x7fd149d410c0 <address@hidden> 0x00007fd149d48b72 <+514>: mov %rax,0x50(%rsp) <<------ Address returned by __errno_location() is stored in a special location in stack for later use. 0x00007fd149d48b77 <+519>: mov (%rax),%eax 0x00007fd149d48b79 <+521>: mov %eax,0x78(%rsp) .... [ERRNO-2] 1281 if (errno != ENODATA) { 0x00007fd149d492ae <+2366>: mov 0x50(%rsp),%rax <<----- Because it already stored the address returned by __errno_location(), it just dereferences the address to get the errno value. BUT THIS CODE NEED NOT BE EXECUTED BY SAME THREAD!!! 0x00007fd149d492b3 <+2371>: mov $0x9,%ebp 0x00007fd149d492b8 <+2376>: mov (%rax),%edi 0x00007fd149d492ba <+2378>: cmp $0x3d,%edi The problem is that __errno_location() value of t1 and t2 are different. So [ERRNO-2] ends up reading errno of t1 instead of errno of t2 even though t2 is executing [ERRNO-2] code section. When code is compiled without any optimization for [ERRNO-2]: 1281 if (errno != ENODATA) { 0x00007fd58e7a326f <+2237>: callq 0x7fd58e797300 <address@hidden><<--- As it is calling __errno_location() again it gets the location from t2 so it works as intended. 0x00007fd58e7a3274 <+2242>: mov (%rax),%eax 0x00007fd58e7a3276 <+2244>: cmp $0x3d,%eax 0x00007fd58e7a3279 <+2247>: je 0x7fd58e7a32a1 <gf_defrag_migrate_data+2287> Fix: Make syncop_xxx() return (-errno) value as the return value in case of errors and all the functions which make syncop_xxx() will need to use (-ret) to figure out the reason for failure in case of syncop_xxx() failures. Change-Id: I314d20dabe55d3e62ff66f3b4adb1cac2eaebb57 BUG: 1040356 Signed-off-by: Pranith Kumar K <pkarampu@redhat.com> Reviewed-on: http://review.gluster.org/6475 Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Anand Avati <avati@redhat.com>
Diffstat (limited to 'api/src/glfs-handleops.c')
-rw-r--r--api/src/glfs-handleops.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/api/src/glfs-handleops.c b/api/src/glfs-handleops.c
index 0f996d3a2da..5bba38b5f0c 100644
--- a/api/src/glfs-handleops.c
+++ b/api/src/glfs-handleops.c
@@ -152,6 +152,7 @@ glfs_h_stat (struct glfs *fs, struct glfs_object *object, struct stat *stat)
/* fop/op */
ret = syncop_stat (subvol, &loc, &iatt);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (!ret && stat) {
@@ -258,6 +259,7 @@ glfs_h_setattrs (struct glfs *fs, struct glfs_object *object, struct stat *stat,
/* fop/op */
ret = syncop_setattr (subvol, &loc, &iatt, glvalid, 0, 0);
+ DECODE_SYNCOP_ERR (ret);
out:
loc_wipe (&loc);
@@ -331,6 +333,7 @@ glfs_h_open (struct glfs *fs, struct glfs_object *object, int flags)
/* fop/op */
ret = syncop_open (subvol, &loc, flags, glfd->fd);
+ DECODE_SYNCOP_ERR (ret);
out:
loc_wipe (&loc);
@@ -420,6 +423,7 @@ glfs_h_creat (struct glfs *fs, struct glfs_object *parent, const char *path,
/* fop/op */
ret = syncop_create (subvol, &loc, flags, mode, glfd->fd,
xattr_req, &iatt);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (ret == 0) {
@@ -518,6 +522,7 @@ glfs_h_mkdir (struct glfs *fs, struct glfs_object *parent, const char *path,
/* fop/op */
ret = syncop_mkdir (subvol, &loc, mode, xattr_req, &iatt);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if ( ret == 0 ) {
@@ -606,6 +611,7 @@ glfs_h_mknod (struct glfs *fs, struct glfs_object *parent, const char *path,
/* fop/op */
ret = syncop_mknod (subvol, &loc, mode, dev, xattr_req, &iatt);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (ret == 0) {
@@ -676,11 +682,13 @@ glfs_h_unlink (struct glfs *fs, struct glfs_object *parent, const char *path)
if (!IA_ISDIR(loc.inode->ia_type)) {
ret = syncop_unlink (subvol, &loc);
+ DECODE_SYNCOP_ERR (ret);
if (ret != 0) {
goto out;
}
} else {
ret = syncop_rmdir (subvol, &loc, 0);
+ DECODE_SYNCOP_ERR (ret);
if (ret != 0) {
goto out;
}
@@ -755,6 +763,7 @@ glfs_h_opendir (struct glfs *fs, struct glfs_object *object)
/* fop/op */
ret = syncop_opendir (subvol, &loc, glfd->fd);
+ DECODE_SYNCOP_ERR (ret);
out:
loc_wipe (&loc);
@@ -846,6 +855,7 @@ glfs_h_create_from_handle (struct glfs *fs, unsigned char *handle, int len,
}
ret = syncop_lookup (subvol, &loc, 0, &iatt, 0, 0);
+ DECODE_SYNCOP_ERR (ret);
if (ret) {
gf_log (subvol->name, GF_LOG_WARNING,
"inode refresh of %s failed: %s",
@@ -934,6 +944,7 @@ glfs_h_truncate (struct glfs *fs, struct glfs_object *object, off_t offset)
/* fop/op */
ret = syncop_truncate (subvol, &loc, (off_t)offset);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (ret == 0)
@@ -1006,6 +1017,7 @@ glfs_h_symlink (struct glfs *fs, struct glfs_object *parent, const char *name,
/* fop/op */
ret = syncop_symlink (subvol, &loc, data, xattr_req, &iatt);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (ret == 0) {
@@ -1081,6 +1093,7 @@ glfs_h_readlink (struct glfs *fs, struct glfs_object *object, char *buf,
/* fop/op */
ret = syncop_readlink (subvol, &loc, &linkval, bufsiz);
+ DECODE_SYNCOP_ERR (ret);
/* populate out args */
if (ret > 0)
@@ -1166,6 +1179,7 @@ glfs_h_link (struct glfs *fs, struct glfs_object *linksrc,
/* fop/op */
ret = syncop_link (subvol, &oldloc, &newloc);
+ DECODE_SYNCOP_ERR (ret);
if (ret == 0)
/* TODO: No iatt to pass as there has been no lookup */
@@ -1256,6 +1270,7 @@ glfs_h_rename (struct glfs *fs, struct glfs_object *olddir, const char *oldname,
/* TODO: check if new or old is a prefix of the other, and fail EINVAL */
ret = syncop_rename (subvol, &oldloc, &newloc);
+ DECODE_SYNCOP_ERR (ret);
if (ret == 0)
inode_rename (oldloc.parent->table, oldloc.parent, oldloc.name,