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H A D | io.c | ffb6b7e4 Tue May 12 07:43:44 CDT 2009 Artem Bityutskiy <Artem.Bityutskiy@nokia.com> UBI: fix races in I/O debugging checks
When paranoid checs are enabled, the 'io_paral' test from the 'mtd-utils' package fails. The symptoms are:
UBI error: paranoid_check_all_ff: flash region at PEB 3973:512, length 15872 does not contain all 0xFF bytes UBI error: paranoid_check_all_ff: paranoid check failed for PEB 3973 UBI: hex dump of the 512-16384 region
It turned out to be a bug in the checking function. Suppose there are 2 tasks - A and B. Task A is the wear-levelling working ('wear_leveling_worker()'). It is reading the VID header to find which LEB this PEB belongs to. Say, task A is reading header of PEB X. Suppose PEB X is unmapped, and has no VID header. Task B is trying to write to PEB X.
Task A: in 'ubi_io_read_vid_hdr()': reads the VID header from PEB X. The read data contain all 0xFF bytes. Task B: writes VID header and some data to PEB X Task A: assumes PEB X is empty, calls 'paranoid_check_all_ff()', which fails.
The solution for this problem is to make 'paranoid_check_all_ff()' re-read the VID header, re-check it, and only if it is not there, check the rest. This now implemented by the 'paranoid_check_empty()' function.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> ffb6b7e4 Tue May 12 07:43:44 CDT 2009 Artem Bityutskiy <Artem.Bityutskiy@nokia.com> UBI: fix races in I/O debugging checks When paranoid checs are enabled, the 'io_paral' test from the 'mtd-utils' package fails. The symptoms are: UBI error: paranoid_check_all_ff: flash region at PEB 3973:512, length 15872 does not contain all 0xFF bytes UBI error: paranoid_check_all_ff: paranoid check failed for PEB 3973 UBI: hex dump of the 512-16384 region It turned out to be a bug in the checking function. Suppose there are 2 tasks - A and B. Task A is the wear-levelling working ('wear_leveling_worker()'). It is reading the VID header to find which LEB this PEB belongs to. Say, task A is reading header of PEB X. Suppose PEB X is unmapped, and has no VID header. Task B is trying to write to PEB X. Task A: in 'ubi_io_read_vid_hdr()': reads the VID header from PEB X. The read data contain all 0xFF bytes. Task B: writes VID header and some data to PEB X Task A: assumes PEB X is empty, calls 'paranoid_check_all_ff()', which fails. The solution for this problem is to make 'paranoid_check_all_ff()' re-read the VID header, re-check it, and only if it is not there, check the rest. This now implemented by the 'paranoid_check_empty()' function. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
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